Browsing by Author "Naidoo, Yougasphree."

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Biosystematic studies in Southern African species of Strychnos L. (Loganiaceae)
(2014) Adebowale, Adekunle.; Nicholas, Ashley.; Lamb, Jennifer Margaret.; Naidoo, Yougasphree.
Strychnos L. is the largest genus of the pantropical or subtropical family Loganiaceae with about 200 species. Their habits range from trees and shrubs in open areas to lianas in rain forests. The genus is well-known as a source of alkaloids such as strychnine and brucine and other allied compounds, all of which have been used medicinally and in curare formulation for centuries. While taxonomic circumscription of the genus has never been contentious, there is no consensus about infrageneric affiliations, the latest of which recognises 12 sections based on morphological characters. Recent molecular evaluation of the genus on a global scale with the internal transcribed spacer (ITS) marker suggests that many of the currently recognised sections are not monophyletic. An understanding of regional patterns of evolution, which is relevant for biodiversity conservation, requires an in-depth study of the focus group on a regional scale. Using a multiplicity of approaches from morphological and molecular to biogeographical, this study is an attempt at elucidating diversity patterns at different levels among the southern African species of Strychnos. Various combinations of morphological attributes from branches, leaves, flowers and fruits distinguish seemingly homologous clusters of species, sometimes supported by molecular data. A lack of molecular support for a hypothetical relationship may viii indicate case(s) of convergent evolution in these features across the taxa involved. Molecular phylogenies based on the ITS and chloroplast markers confirm the nonmonophyletic nature of all but section Spinosae. Proposals for sectional recircumscriptions of the genus are provided. Patterns of speciation within Strychnos suggest a Miocene origin in the rain forests along the South America/Guinea-Congolian axis. Within the southern African subcontinent, the evolution of the genus carries a strong ecological signature along either the forest or savanna biome, with many accompanying morphological adaptations for the respective habitats. The non-synonymy of S. gerrardii with S. madagascariensis is demonstrated with multiple sources of data, as a case of integrative taxonomy succeeding where single-source data approaches might have failed. Routes to current distribution of the genus in southern Africa are hypothesised to involve a combination of palaeo-climatic oscillations and allopatric speciation, consistent with the process indicated in many other plant groups for the region. The findings are discussed in the wider context of their implications for taxonomy and biodiversity conservation in the face of climate change, food security and other relevant issues in systematics.
Ecophysiological studies of the invasive weed Chromolaena odorata (L.) King and Robinson and its control in KwaZulu-Natal.
(2013) Naidoo, Kubendran Kista.; Naidoo, Gonasageran.; Naidoo, Yougasphree.
Despite increased interest in the control and spread of the alien weed, Chromolaena odorata, little is known of its photosynthetic characteristics under field conditions. The aim of the study was to obtain a better understanding of the ecophysiological attributes of C. odorata that contribute to its invasive success. Photosynthetic performance of C. odorata was evaluated by monitoring diurnal changes in gas exchange, chlorophyll a fluorescence and plant water relations. Gas exchange characteristics of plants growing in exposed and shaded environments, as well as seasonal patterns, were evaluated. The response of C. odorata to water stress was also determined. Chromolaena odorata exhibited high CO2 uptake rates with no light saturation. Shade plants had significantly larger leaf surface areas and greater concentrations of total chlorophyll, total carotenoids and chlorophylls a and b than sun plants. Relatively high photosynthetic uptake rates in C. odorata may allow for greater carbon gain in high light environments thus contributing to increased growth and spread of the species. Chromolaena odorata can successfully acclimatise to low photosynthetic photon flux density (PPFD), thus, outcompeting less tolerant species under low light conditions. Leaf conductance, CO2 uptake, transpiration and chlorophyll fluorescence parameters in winter were tightly coupled to summer. Plants had higher water use efficiency (WUE) in summer compared to winter, probably to maximise CO2 uptake and minimise water loss. There was a progressive decrease in leaf water potential with increase in water stress in water stressed (WS) plants. The leaves of WS plants showed signs of severe wilting 10 days after the onset of stress compared to well watered (WW) plants. Increased proline concentration and leaf wilting probably increase (WUE) and may be an adaptive strategy to protect against dehydration injury.The effects of the herbicide, glyphosate, on gas exchange and translocation were studied. Glyphosate treatment decreased leaf conductance leading to a reduction in CO2 uptake and transpiration. Glyphosate is a mobile herbicide that is transported from leaves to roots and caused death of plants within a week of treatment. The potential antimicrobial properties of the weed were evaluated using selected bacteria and fungi. Crude leaf extracts exhibited some antibacterial and antifungal activity. Extracts from the weed are unlikely to be useful antimicrobial sources due to low concentrations of active compounds. A co-ordinated strategy, taking into account the high plasticity of the weed, is needed to curtail the spread of C. odorata. The ecophysiological responses to environmental conditions should be considered when planning management and control strategies for C. odorata.
The effects of petroleum hydrocarbon contamination on selected intertidal macrophytes and meiofauna.
(2015) Naidoo, Krishnaveni.; Naidoo, Gonasageran.; Naidoo, Yougasphree.
The effects of bunker fuel oil on the growth of A. marina, B. gymnorrhiza and R. mucronata were investigated in glasshouse and field experiments. The effects of oil on community structure in micro-organisms were also investigated in microcosm glasshouse experiments. The differences in oil tolerance of the three mangroves were compared in propagule and sediment oiled treatments and growth monitored for 13 months under glasshouse conditions. In propagule oiled treatments, various portions of the propagule were coated with oil. In the sediment oiled treatments, 50ml oil were added to the sediment in each pot. In oiled treatments, plant height, number of leaves and chlorophyll content were significantly reduced in all species compared to the control. In A. marina and R. mucronata, oiling resulted in growth malformations such as abnormal phyllotaxy and deformity of leaves and stems. The effects of oil on root growth were investigated in rhizotrons for 245 and 409 days respectively. In oiled treatments, root growth rate, length and volume were significantly reduced in all species. In A. marina and B. gymnorrhiza oil increased root diameter. In another series of experiments, PAH accumulation in roots and leaves of the three species were determined in one year old seedlings subjected to oiling for 21 days. The concentrations of 15 PAHs in roots and leaves were determined by gas chromatography / mass spectrometry. The highest total concentration of PAHs was accumulated in oiled roots of A. marina (44,045.9μg/kg), followed by B. gymnorrhiza (10,280.4μg/kg) and R. mucronata (6,979.1μg/kg). In oiled treatments, the most common PAHs in roots of all species were fluorene and acenaphthene (two rings), phenanthrene and anthracene (three rings), pyrene and chrysene (four rings) and benzo[a]pyrene (five rings). In the leaves of all species in oiled treatments, the common PAHs were naphthalene and acenapthene (two rings) and phenanthrene (three rings). To test for living and dead root tip cells and to compare the effects of oil on cell ultrastructure in roots and leaves of the three species, one year old seedlings were subjected to a control and sediment oiled treatments for seven days. Control root tips, stained with fluorescein diacetate, exhibited green fluorescence in living cells of the meristematic and conducting tissue in all species. Oiled root tips, stained with propidium iodide, exhibited red fluorescence, indicating cell death or dead cells. Transmission electron micrographs revealed that oil damaged cell ultrastructure in root tips and leaves in all species. Anatomical changes induced by oil included, disorganization of cells in the root cap, epidermis and meristem. Oil also induced loss of cell contents and destruction of organelles in root tissue. Oil damaged chloroplasts and cell organelles in spongy mesophyll and palisade cells of leaves. To compare the effects of oil on the ability of the three species to tolerate salinity, healthy one year old seedlings were subjected to 10% and 50% seawater in control and sediment oiled treatments for 12 months. In the oiled treatments, 200ml oil were added to the soil in each pot. Oil significantly reduced growth in the 50% seawater treatment in all species. Results suggested that oil reduces salt tolerance in the three species. The effects of oil on salt secretion in A. marina were investigated by subjecting one year old seedlings to sediment oiling treatments at 0%, 10% and 50% seawater for three weeks. Sodium accumulated in the leaves of oiled seedlings at 10% and 50% seawater. The effects of oil on salt secretion in A. marina in the light and dark were compared in one year old seedlings subjected to oiling treatments for seven days. Sodium accumulated in the leaves of oiled seedlings in the light and dark within 11 hours. Oil reduced secretion rates of Na⁺, K⁺, Ca²⁺ and Mg²⁺ in all treatments. The effects of oil on species abundance, richness and community structure of soil micro-organisms were determined by subjecting microcosms to oiling treatments with or without fertiliser for four weeks. In the oiled treatments, 15ml oil and 5ml/L fertiliser were added to 200g soil. Fertiliser consisted of 4% N, 2% P and 5% K. Nematodes were extracted after the experimental period and identified to genus or species level. Oil significantly reduced species abundance and richness. Oil also eliminated sensitive species and altered the abundance of dominant species thereby altering the free living nematode community structure. Addition of fertiliser increased richness and dominant species in oiled treatments. The effects of oil coating on leaves and internodes on growth of the three mangroves were investigated in field experiments for 48 weeks. Oiling of the leaves resulted in leaf abscission and decreased leaf production in all species. The effects of sediment oiling (at a dose of 5Lmˉ²) on the three species were also investigated in a field study for 53 weeks. In A. marina, oil caused adventitious roots to develop on the stem, about 10-15 cm above the soil surface after 38 weeks of treatment. In oiled treatments, plant mortality occurred after 53 weeks in all three species. The ability of B. gymnorrhiza and R. mucronata to exclude PAHs from sensitive root tissues probably accounted for the higher oil tolerance than A. marina. The capacity of the species to adapt to residual oil contamination by increasing root diameter (A. marina and B. gymnorrhiza), producing adventitious roots (A. marina), increasing root/shoot ratio (R. mucronata) and abscising oiled leaves (all species) probably contributed to oil tolerance.
The foliar micromorphology and medIicinal phytochemicalpProperties of Heteropyxis Natalensis (Myrtaceae).
(2018) Chetty, Saiyuri Dayinee.; Naidoo, Yougasphree.
The use of medicinal plants as a form of therapeutic healing is an ancient tradition in various regions of the world. As a result, there is a dire need to screen medicinal plants for their unrevealed pharmacological potential. The foliar micromorphology of plants enables researchers to investigate the synthesis and location of medicinal phytocompounds. Heteropyxis natalensis is a South African medicinal plant and is traditionally used in Venda and Zulu communities to treat several illnesses. This study aimed to characterise the foliar structures of H. natalensis leaves, locate the site of secondary metabolites, determine the phytochemical composition of the leaves, and investigate the antibacterial efficacies and silver nanoparticles (AgNPs) of the methanolic extract. Emergent, young and mature leaves were examined using various microscopy techniques which confirmed the presence of non-glandular trichomes as the main external appendages of the leaves. Micrographs also revealed internal secretory cavities and crystal idioblasts. Secretory cavities were observed accumulating amorphous secretions and histochemical tests detected alkaloids, phenolics, essential oils and lipids. Qualitative phytochemical analyses were conducted on hexane, chloroform and methanol leaf extracts, and detected phenolics, alkaloids, saponins, sterols and terpenes. Crude methanolic extract was further examined using gas chromatographymass spectrometry and identified several important bioactive compounds of pharmacological value. A “green approach” was used to synthesise AgNPs using the methanolic leaf extract. Characterisation studies identified spherical particles below 100 nm in size, as well as the functional groups responsible for the capping of silver ions (Ag+). The crude methanolic extract and AgNPs were screened for their antibacterial efficacy and showed inhibition of five pathogenic bacterial strains. The results obtained in this study revealed that the phytochemical compounds present in H. natalensis leaves justify the use of this species in traditional medicine.
Foliar secretory cavities of Vepris lanceolata (Lam.) G. Don (Rutaceae): micromorphology and chemical composition of the secretion.
(2017) Nxumalo, Nozipho Ntombikayise.; Naidoo, Yougasphree.; Naidoo, Gonasageran.
Secretory structures such as ducts, trichomes and cavities consist of cells that are primary sites synthesizing essential oils and other phytochemical compounds with medicinal properties. Little is known about the micromorphology of secretory structures and the composition of the chemical constituents. There was no information documented on the micromorphology of secretory structures of Vepris lanceolata (Lam.) G. Don (Rutaceae family). The aim of this research was to investigate the micromorphological characteristics of foliar secretory cavities, the chemical composition of the secretion, and the antibacterial activity of leaf extracts of Vepris lanceolata. Scanning electron microscope (SEM) images by chemical fixation and freeze drying revealed no external secretory structures on the surfaces of leaves. SEM images by freeze-fracture showed secretory cavities present in the leaf blade. The cavities were embedded amongst palisade and spongy parenchyma cells, next to the vascular bundle. Cavities were made up of the lumen surrounded by varying layers of epithelial cells, depending on the secretory phase of the cavity. Semi-thin and ultra-thin sections showed that foliar cavities develop schizo-lysigenously, i.e. cavities develop by both separation and degradation of epithelial cells. Transmission electron microscope (TEM) sections showed that during the secretory stage, secretory cells contained oil droplets, vacuoles and vesicles indicating active secretion. Histochemical assays of fresh leaves showed the localization of phytochemical compounds. Cavities turned orange red when stained with Sudan III indicating the presence of lipids and pink with NADI reagent to show essential oils. Cavities also stained positive for polysaccharides, sugars, phenolic compounds, proteins and alkaloids. Phytochemical screening showed the presence of alkaloids, glycosides, carbohydrates, proteins, tannins, phenolic compounds, flavonoids, fixed oils and fats. Preliminary thin layer chromatography (TLC) showed separation of bands indicating groups of active compounds in leaf extracts. Crude (ethanolic and methanolic) and water extracts of leaves showed antibacterial activity against gram positive bacteria Staphylococcus aureus (ATCC 25923) and methicillin-resistant Staphylococcus aureus (ATCC BAA-1683); and five strains of gram-negative bacteria: Escherichia coli (ATCC 25922), Escherichia coli (carbapenem-resistant) (ATCC BAA 2340), Klebsiella pneumonia (ATCC 314588), Pseudomonas aeruginosa (ATCC 27853), as well as Salmonella typhimurium (ATCC14026) according to the disc diffusion method. Leaf extracts have tannins, alkaloids, flavonoids, essential oil and flavonoids responsible for the antimicrobial activity of the plant.
Histo-phytochemical evaluation and characterisation of the foliar structures of Tagetes minuta L. (Asteraceae).
(2018) Rikisahedew, Jesamine Jöneva.; Dewir, Yaser Hassan.; Naidoo, Yougasphree.
Plants have been used as ethnomedicine for millennia. In recent years, there has been an upward surge of interest in the use of plants as medicine due to the interest in drugs with fewer side effects as well as the fight against antibiotic resistance. This study is based on Tagetes minuta, an aromatic essential herb that is cultivated for its high percentage essential oils which have been used in the treatment of various ailments. In addition, T. minuta contains a myriad of secondary metabolites that serve in numerous industrial and clinical applications. The aim of this study was to characterise the foliar structures responsible for the production, storage, and exudation of these useful compounds, as well as to examine the chemical constituents of the crude organic solvents derived from the leaves of T. minuta. The potential for green synthesis of silver nanoparticles from the crude methanolic extract and its potential as an antibacterial was also determined. Stereomicroscopy and scanning electron microscopy revealed the presence of uniseriate non-glandular trichomes on the foliar surfaces, as well as large pellucid secretory cavities. Histochemical analyses on the non-glandular trichomes showed that they are capable of storing various bioactive compounds, which is a novel discovery for this species. The development of the subdermal secretory cavities show that the cells undergo autolysis in order to form a schizolysigenous cavity in mature leaves, which was revealed using light microscopy. The ultrastructure of the secretory epithelium within the secretory cavity was analysed using transmission electron microscopy, which displayed the changes of the plastids to contain lipid molecules as well as an increase in vesicles indicating the presence of essential oils. Phytochemical analysis on the crude organic solvents derived from the leaves of T. minuta revealed the presence of alkaloids, sterols, saponins, terpenoids, phenols, and lipids. Gas-chromatography mass-spectrometry was carried out to reveal that the constituents with the highest percentage were 9-octadecen-1-ol (4.51 %), β-sitosterol (6.07 %), olean-12-en-3-one (7.47 %), and 3-methyl-1-butanol (14.77 %), all of which cause bacterial growth inhibition, as well as showing acaricidal activity, and anticancer properties in studies focussed on clinical applications. Silver nanoparticles were successfully synthesised from the methanolic leaf extract, which was confirmed using UV-visible spectroscopy and energy dispersive x-ray analysis. UV–visible spectrum of synthesised silver nanoparticles showed maximum peak at 442 nm, and transmission electron microscopy revealed the silver nanoparticles to be spherical in shape, ranging from 10 to 50 nm in diameter. Preliminary antimicrobial activity was determined using the agar well diffusion method, which showed growth inhibition against E. coli, S. aureus, methicillin-resistant S. aureus, B. subtilis and P. aeruginosa. This study has shown that T. minuta contains numerous bioactive compounds that have pharmacological and medicinal uses, as well as characterising the non-glandular trichomes present on the adaxial and abaxial leaves for the first time. The synthesis of silver nanoparticles from the methanolic extract of T. minuta in this study is novel, and shows promise for cheaper, more effective, and less risky nanotechnological applications.
The leaf secretory apparatus of Hibiscus surattensis and Hibiscus sabdariffa (Malvaceae) : micromorphology, histo-phytochemistry and ultrastructure.
(2015) Raghu, Kashmira.; Naidoo, Yougasphree.; Nicholas, Ashley.
The research presented here forms the basis of the ethnobotanical and ethnopharmacological evaluation of Hibiscus surattensis, which is a widely distributed vegetable and medicinal shrub used by African and Indian traditional practitioners. Using light microscopy together with advanced electron microscopy techniques, the leaf topography and internal structure was examined. A closely related species, Hibiscus sabdariffa was also investigated for foliar and histophytochemical comparisons. Hibiscus sabdariffa is a widely consumed medicinal species with well-known biological activity and known chemical principles. Both species belong to the section Fucaria within the genus Hibiscus. Analyses of foliar secretory tissues showed that both H. surattensis and H. sabdariffa were characterised by capitate trichomes as well as mucilage-producing ducts and idioblasts. Head cells of capitate trichomes were between 5 and 7, while lignified stalk cells occurred in numbers of 2 or 3. A basal cell supporting the trichome was implanted in the epidermis comparative study between the two species showed some variation of chemical composition in trichome head cells. Polysaccharidic, alkaloids, phenolic and acidic lipid components were identified for both H. surattensis and H. sabdariffa whereas H. sabdariffa showed an intense staining of proteinaceous substances. Densities of capitate trichomes varied from emergent to mature developmental stages, with the highest number occurring on the emergent abaxial surface for both H. surattensis and H. sabdariffa. However, a distinct trend was observed for H. surattensis, where a decrease in capitate trichomes with progressive development was associated with the proliferation of mucilage idioblasts, particularly on the mature adaxial surface. Mucilage producing tissues are assumed to be associated with a protective role against dehydration in a number of plant families. Idioblasts observed in H. surattensis were visible leaf surface structures, embedded in the epidermal tissues. They contained considerable amounts of acidic polysaccharides and acidic lipids, and appeared to be implicated in reducing evaporative water loss in fully expanded leaves. Mucilage ducts were identified in vascular tissue within leaf veins. They occurred parallel with the conducting tissue and comprised of an epithelial layer of cells which seemed to be secreting a mucilage into an extracellular lumen. Crystal idioblasts were also identified in tissues of both H. surattensis and H. sabdariffa. The sequestration of calcium oxalate is assumed to be governed and regulated by specialised mesophyllous idioblasts that in turn appeared to be triggered by excess calcium within the plant body to differentiate into crystal forming cells. The supposed function of calcium oxalate crystals includes mechanical support and herbivory avoidance. TEM revealed the cellular processes which involved crystal idioblast development in H. surattensis. This appeared to demonstrate that degeneration of organelles which are assumed to occur when crystals reach maximal proportions. The non-glandular trichome component of each Hibiscus species was diverse in trichome type and might have accounted for differences in leaf texture and the leaf indumentum. The prickly texture of Hibiscus surattensis was attributed to rigid stellate and falcate trichomes as well as restrorse prickles, whereas the leaves of H. sabdariffa were glabrous with few falcate, bi- and trifurcate trichomes found mainly at the base or along the midvein. Preliminary phytochemical experiments which involved methanolic, chloroform and hexane extracts, yielded favourable results, which showed that leaves of H. surattensis and H. sabdariffa were chemically similar, in this regard, the author recommended further investigation into the phytochemical nature of H. surattensis.
Leaf ultrastructural studies of Avicennia marina in response to salinity under natural conditions.
(2007) Hiralal, Omitha.; Naidoo, Gonasageran.; Naidoo, Yougasphree.
In Richards Bay Harbour, the mangrove Avicennia marina exhibits a distinct natural productivity gradient. The fringe site, which is regularly inundated twice daily by tides, supports luxuriant adult A. marina trees that are 6-10 m tall and which form a dense, well-developed canopy. The landward site which is only inundated during high spring tides, supports diminutive or dwarf A. marina that are less than 1.5 m in height. In this study we compared leaves from fringe and dwarf sites with respect to morphology, ultrastructure and ecophysiology. Alterations in leaf morphology, ultrastructure and physiology of A. marina were compared at the fringe site (35 ‰) and dwarf site (60 ‰) using morphometric measurements, light (LM), transmission (TEM) and scanning microscopy (SEM). SEM and light microscopy revealed that multicellular salt glands were located on the thick, cutinised adaxial surface from leaves of both sites. The glands appeared to be scattered and protruding from individual crypts in fringe mangrove leaves whilst they appeared sunken and occluded by cuticular material in dwarf mangrove leaves. The salt glands on the abaxial surface were not sunken but obscured by the indumentum of peltate trichomes. Ultrastructural changes observed in dwarf mangrove leaves were associated with cuticle, cell walls, chloroplasts, mitochondria of mesophyll tissue and salt glands. Fringe mangrove leaves had chloroplasts with typical well-developed grana and stroma. Ultrastructural changes of chloroplasts were evident in dwarf mangrove leaves and included swelling and separation of thylakoids, disintegration of granal stacking and integranal lamellae, as well as loss of the integrity of the chloroplast envelope. Multivesicular structures were commonly found in vacuoles and associated with chloroplasts and mitochondria in both leaf types. In fringe mangrove leaves, mitochondria appeared spherical to tubular with a relatively smooth outer membrane and a highly convoluted inner membrane. Swelling and vacuolation of mitochondrial membranes, cristae and mitochondrial clustering in the cytoplasm around the chloroplasts were evident in dwarf mangrove leaves. Extensive lipid accumulation in the form of large, dense plastoglobuli occurred in the chloroplasts of dwarf mangrove leaves. There were characteristic differences in salt gland morphology of fringe and dwarf mangrove leaves, namely in the cell walls, vacuoles, and vesicle formation. In salt glands of dwarf mangrove leaves, a distinct withdrawal of the cytoplasm from the cell wall was observed. This feature was not observed in salt glands of fringe mangrove leaves. Numerous large vacuoles were observed in the secretory cells of glands of dwarf mangrove leaves compared to those of fringe plants. Multivesicular structures, vesicles and mitochondria were common features in both leaf types. Physiological studies involved a comparison of osmotic and ionic relations as well as whole plant responses in fringe and dwarf mangrove leaves. Relative leaf water content decreased by 7.8 % and specific leaf area by 17 % in dwarf compared to those of fringe mangroves. Dwarf mangrove leaves were 27.6 % thicker and leaf cuticle thickness 37.4 % higher than those from fringe mangroves. Fringe mangrove leaves displayed higher total chlorophyll contents by 27 %, with chlorophylls a and b being 22 % and 39.6 % higher, respectively than those of dwarf mangroves. Salt gland frequencies were higher in the apex, mid-lamina and base of fringe than dwarf mangrove leaves by 36 %, 45 % and 51 %, respectively. The concentration of glycinebetaine, a compatible, N-containing osmolyte was significantly higher by 40 % in dwarf than in fringe mangrove leaves. Concentrations of proline were 27 % lower in dwarf than in fringe mangrove leaves. The predominant inorganic ion detected in mature leaves was Na+, which was 19 % higher in dwarf than fringe mangrove leaves. Phosphorus was an element that appeared deficient in dwarf mangrove leaves, being 50 % lower compared to fringe mangrove leaves. The results of this investigation indicated that there were cytomorphological alterations as well as differences in physiological responses in leaves of A. marina at fringe and dwarf sites.
Medicinal properties and micromorphology of Rauvolfia caffra Sond.
(2017) Govender, Valentina.; Naidoo, Yougasphree.; Naidoo, Gonasageran.
Medicinal plants are effective treatments for various ailments and conditions due to the fact that they are easily accessible, cost effective, trusted and have little to no side effects. Plants produce bioactive or secondary compounds that serve as a defence mechanism to deter pests, attract pollinators and continue to assist in the survival of the species. These compounds or phytochemicals are useful to humans in the form of natural medicine, Rauvolfia caffra Sond. (Apocynaceae) is no exception. The traditional use of the bark is to alleviate skin ailments. A decoction of the bark is consumed for the treatment of abdominal discomfort, abscesses, pneumonia and fever. The research problem is that R. caffra has not been fully documented and the traditional uses cannot be supported scientifically. Furthermore, micromorphological characteristics remain to be described. This is a key component since R. caffra synthesizes latex and transports it through laticifers. The micromorphological characteristics were described by stereomicroscopy, scanning electron microscopy, light microscopy and histochemical tests on the leaves and petioles. This detected the presence of laticifers. To investigate the medicinal value, preliminary phytochemistry and antibacterial screening was performed on crude extracts of the stems and leaves. Methanol, chloroform and hexane were used as solvents of extraction and the classes of compounds detected were alkaloids, glycosides, sterols, flavones and flavonones. Thin layer chromatography provided a visualization of the classes of compounds present. The methanolic stem extract was found to inhibit seven strains of bacteria including E. coli and methicillin-resistant Staphylococcus aureus. The findings do not discredit the traditional utilization of this plant. Additionally, silver nitrate was combined with the crude methanol and water extracts of the stem and leaves to determine if silver nanoparticles (AgNPs) can be formed using a protocol that is safe, not toxic to the environment and simple to carry out. Three different mixing ratios (1:1, 1:2 and 1:4) were used to discover the optimum conditions for synthesis and the extracts screened for their antibacterial activity. The AgNPs synthesized ranged from15.84nm to 34.99nm in diameter which falls within a range that is preferred in nanoscience. The water stem 1:4 AgNPs was found to inhibit two different strains of bacteria, viz. methicillin-resistant Staphylococcus aureus and Klebsiella pneumonia. Rauvolfia caffra does have the potential to be used in drug formulation and in nanotechnology to treat prevalent health problems in South Africa.
Microbial community study of brine evaporation ponds: identification and analysis of the total organic carbon problem.
(2021) Rambaran, Vrishthi.; Nemukula, Aluwani.; Joslin, Paul Anthony.; Naidoo, Yougasphree.
Salt is an important compound as it is used by humans for everyday life. Salt production can occur from two processes: the use of seawater which is evaporated leaving the salt behind or the use of brine which is obtained from underground sources and undergoes the same process of evaporation as the seawater. The focus for this research will be on the microorganism population in salt produced from underground brine sources such as the source used by Botswana Ash (Pty) Ltd (Botash) which is the salt works that provided the samples for this research paper. The most important microorganism found in salt evaporation ponds is the green algae Dunaliella salina (D. salina) as discovered by previous studies. The main focus of this study was the identification of the microorganisms that are found within the salt evaporation ponds and the effect that the dominant D. salina population will have on the salt production process and also whether the dominant D. salina species can be used for production of important by-products to generate another source of income. The population genetics study on the samples from the various evaporation ponds at Botash has revealed the presence of many different microorganisms such as the bacterium Salinabacter, and the green algae Dunaliella salina which was revealed to be the dominant species. Other species such as archaea were also discovered within the salt evaporation ponds at Botash. The green algae D. salina was focused upon due to its dominance within the higher salinity ponds where it serves as the primary producer. The growth rate of the dominant D. salina species was observed in different conditions such as saline concentrations and different nitrogen sources. The results found that D. salina grows best at 3M salinity with NO3 or Urea as the nitrogen source. A study of the growth of D. salina when environmental factors were controlled showed that D. salina prefers high temperatures and high saline conditions for growth. D. salina also produces high value products such as beta carotene and Extra Polysaccharides (EPS). The production of these compounds are linked to the environmental conditions as it was found that beta carotene production is optimized when the cells are placed under stress during nitrogen starvation. EPS production occurs under all environmental conditions. The results from this research paper show that if the microbial community is controlled and optimized useful by-products can be produced, whilst minimal harm is done to the quality of salt produced.
The micromorphological and essential oil status of the foliar secretory structures of Ocimum obovatum E. Mey. ex Benth. subsp. obovatum (Lamiaceae)
(2011) Kasim, Nazeera.; Naidoo, Yougasphree.; Nicholas, Ashley.
Ocimum obovatum E. Mey ex Benth. var. obovatum is a traditionally used medicinal plant that grows along the KwaZulu-Natal coast and the western Cape of South Africa. The plant is noted for its hair restoration properties, remedy for infantile abdominal pain and cramps and its use as an enema to treat epigastric conditions in children. The aims of this study were to document the micromorphology and ultrastructure of the foliar secretory structures responsible for the production and secretion of the essential oils and chemical composition of the secretion, which gives the plant a distinct aroma. It is believed that these oils contain the active ingredients that contribute to the medicinal properties of the plant. A variety of microscopic methods and histochemical and phytochemical tests were used to achieve this. Leaves in all stages of development were pubescent and gland dots, characteristic of plants in the genus, were found on both adaxial and abaxial surfaces. Three types of trichomes were found on both leaf surfaces across all stages of development; non-glandular trichomes and two types of glandular trichomes. Non-glandular trichomes are single, multicellular and uniseriate with microornamentation and a supportive cellular pedestal. The glandular trichomes consisted of peltate and capitate trichomes. Peltate trichomes are made up of four head cells and a very small basal cell that gives the glands the appearance of being sessile. The capitate trichomes were further divided into two types based on the morphology of the glands. Type I capitate trichomes are smaller than the larger peltate trichomes and are composed of one basal cell and a head consisting of two broad head cells. Type II capitate trichomes consisted of one basal cell, one stalk cell and a single oval head cell. Histochemical tests showed that peltate and Type I capitate trichomes have cutinized or suberized walls in the stalk cell to prevent the apoplastic flow of secretory material into neighbouring mesophyll tissue. The histochemical stains also showed that the secretory material present in the glandular trichomes are lipid in nature and essential oils are present. Ultrastructural studies showed polymorphic leucoplasts, few Golgi bodies, numerous vesicles and mini vacuoles, mitochondria and short profiles of endoplasmic reticulum cisternae. Phytochemical tests revealed the presence of essential oils that are terpene-rich. Flavonoids, tannins, saponins, terpenoids, fixed oils and fat, phenolics and cardiac glycosides were also detected in a crude ethanolic extract of the leaves. These chemical compounds appear to be responsible for the medicinal properties for which the plant is traditionally exploited.
Micromorphology and phytochemistry of the foliar secretory structures of Stachys natalensis Hochst. and development of an in vitro propagation protocol.
(2014) Kalicharan, Benita.; Naidoo, Yougasphree.; Nakhooda, Muhammad.
Many members of the genus Stachys have been used as ornamental plants, or as edible foods and, in a number of cultures, as traditional medicine. One such species, Stachys natalensis Hochst., is a perennial, straggling shrub with aromatic leaves that are covered with hairs. Despite its widespread use for a number of reasons, little information has been available on this plant thus far, its foliar secretory apparatus, or the nature and potential therapeutic value of these secretions. Hence, the aims and objectives of the present study were to elucidate key micromorphological features of the leaf secretory structures of S. natalensis, using both light and electron microscopy and to determine the location and chemical composition of the exudates using various histochemical and phytochemical techniques. An additional aim was to establish an in vitro micropropagation protocol for the sustained and high-yielding production of this elusive and often difficult to cultivate species. Furthermore, the foliar micromorphological fidelity between field and in vitro propagated material was compared. Electron micrographs indicated the presence of glandular and non-glandular trichomes on both abaxial and adaxial foliar surfaces of field grown plants. Greater trichome density was observed on the abaxial surface with trichome distribution decreasing as the leaf developed (p<0.05). Uniseriate, unbranched and striated non-glandular trichomes, present on the foliar surfaces of S. natalensis are known to play a role in physical plant defence mechanisms against herbivory. The presence of an elevated cellular pedestal and striated micro-ornamentation on the stalk served as characteristic features of the non-glandular trichomes. Peltate and capitate glandular trichomes were also identified on the foliar surfaces across all developmental stages. Peltate glands consisted of a short stalk and a multicellular head containing two to eight secretory cells. Two types of capitate trichomes were observed. Type I capitate trichomes consisted of a striated stalk, cutinized neck cell and bulbous head which may be uni- or bi-cellular;Type II capitate trichomes were comprised of a wide base, long and tapering, septate stalk, neck cell and a multicellular secretory head cell. The process of secretion differed between the peltate and capitate glandular trichomes. The peltate and Type II capitate trichomes included a porose cuticle which facilitated the release of secretion to the exterior. Cuticular rupture at weak points of the equatorial plane of the secretory head was observed in Type I capitate trichomes. Qualitative histochemical staining of leaf sections and preliminary phytochemical tests revealed the presence of alkaloids, lipid components, terpenoids and complex polysaccharides concentrated in the glandular trichome head cells and leaf crude extracts, respectively. The perceived therapeutic benefits of this plant are likely to lie within this suite of secondary metabolites. Stachys natalensis plant extracts also contained considerable levels of total phenolic compounds (3.43 ± 0.01 mg GAE/g dry material) and flavonoids (3.04 ± 0.01 mg QE/g dry material). The methanolic extracts demonstrated significant free radical scavenging ability (49.49 ± 3.87 ug/ml) which indicates the potential for its use as a natural antioxidant. In vitro propagation protocol using axillary bud explants was developed for this species. A multi-step decontamination treatment involving explant immersion in 1% and 3% NaClO, followed by 0.1% HgCl₂ was the most efficient method for explant decontamination, resulting in overall explant survival of 48%. All media preparations resulted in > 70% bud break within three weeks with cultures initiated on Medium C ( MS supplemented with 0.5 mg/l BAP and 0.5 mg/l IBA) showing the highest percentage of bud break. Growth medium B (0.5 mg/l kinetin and 0.5 mg/l IAA) showed the greatest total shoot multiplication, number of shoots/explant (9.1 ± 3.6) and height/explant (50.2 ± 5.0 mm) compared to other PGR combinations after 12 weeks. The addition of exogenous auxin (2 mg/l IAA) to MS medium allowed for 64% of plantlets to produce adventitious roots in five weeks, after which rooted plants were acclimatized. Acclimatized plantlets (92 ± 4.2 %) did not show any gross morphological abnormalities compared to field-grown plants, apart from the presence of visibly longer non-glandular trichomes. The peltate and both subtypes of capitate glandular trichomes of acclimatized plants were morphologically similar to their field-grown counterparts. Trichome density on acclimatized plants was greater on the abaxial surface of emergent leaves and this density decreased with leaf maturity, as was observed with field-grown plants. This study appears to be the first investigation of the micromorphology of the foliar structures of S. natalensis. Future studies on morphological aspects of secretory structures should include cytochemical investigations to determine the exact mechanism and origin of glandular secretions. Further analyses regarding the composition of the glandular essential oils and its potential pharmacological efficacy are required. With an effective in vitro propagation protocol being presently established, further optimisation with respect to the type and concentration of exogenous PGRs, explant type or even various routes of organogenesis can be investigated. This may provide a means of enhancing plantlet production, maintaining superior-selected genotypes, and thus potentially maximising the yield of putative pharmacologically-important secondary metabolites.
The morphology and chemical composition of the trichomes of Withania somnifera (Solanaceae)
(2014) Munien, Prelina.; Naidoo, Yougasphree.; Naidoo, Gonasageran.
For centuries, plants have been used in the cosmetic, culinary and medicinal industries. Recently however, the use of plants in the medicinal industry has increased due to the widespread awareness of the harmful effects of synthetic drugs on humans. Withania somnifera (Dunal.) is an evergreen perennial shrub found in the drier parts of Africa, particularly South Africa and Asia. Since the phytochemical compounds within the extracts of W. somnifera act upon both the nervous and reproductive systems, it is used to treat a wide variety of ailments such as arthritis, stress, ulcers, and tremors. This species has therefore been cultivated to extract the phytochemicals produced. The aim of this study was to characterise the micromorphology of the foliar trichomes of W. somnifera as well as to elucidate the location and composition of the secretory products. Stereomicroscopy and scanning electron microscopy (SEM) were used to characterise the foliar trichomes. A series of histochemical and phytochemical tests were performed to determine the location and composition of the compounds that are responsible for the healing properties of the extracts of W. somnifera. Trichome density and length was also determined in three developmental stages of the leaves. Histochemically stained leaf sections and SEM showed the presence of four morphologically distinct trichome types: glandular capitate, non-glandular dendritic, non-glandular bicellular and non-glandular multicellular. Uniseriate, glandular capitate trichomes consisted of a six-celled secretory head, single-celled stalk and a single basal cell. Secretions from the glandular heads of capitate trichomes were visible on the leaf surface during ESEM and histochemical staining. Non-glandular dendritic trichomes, which appeared to emanate from single basal cells, consisted of 2-4 celled stalks and varying branch numbers. These dendritic trichomes exhibited cuticular warts which are involved in the “Lotus-Effect”. Uniseriate, non-glandular bicellular and multicellular (3-6 cells) trichomes also appeared to emanate from single basal cells. Glandular capitate and non-glandular dendritic trichomes were aggregated on the mid-vein of young and mature leaves, possibly to protect underlying vasculature. Histochemical staining and phytochemical testing revealed the presence of two major phytochemical compounds of medicinal importance, i.e. alkaloids and phenolic compounds. These compounds are used to treat a wide variety of ailments, such as dysentery, TB, paralysis, asthma and inflammation, and also act as chemical deterrents in plants. The results of this study explain possible roles of glandular capitate, non-glandular dendritic, non-glandular bicellular and non-glandular multicellular trichomes based on their morphology and foliar distribution. Future studies should aim at determining the biosynthetic pathways, as well as the modes of secretion of alkaloids and phenolic compounds.
Morphology, phytochemistry, and medicinal properties of South African Mangifera indica L. leaves for summer and winter seasons.
(2021) Maharaj, Arvish.; Naidoo, Yougasphree.; Dewir, Yaser Hassan.
Herbal preparations of plants continue to present mankind with novel remedies as many of these plants contain important secondary metabolites. Plant species of the family Anacardiaceae are rich in bioactive phytochemicals. Mangifera indica (Anacardiaceae) is an introduced and naturalised species to South Africa. Herbal use of this plant has not been fully documented; however, it is used in traditional medicine. This study aimed at characterizing the morphology, phytochemistry, and biological activity of Mangifera indica leaves harvested in winter and summer. The foliar biology of the plant was conducted by various microscopy techniques such as stereo- and Scanning electron microscopy. The length and diameter of the different trichome types were measured using ImageJ. The non-glandular trichome lengths range between 70 - 200 μm. The peltate gland trichomes consist of 2 rows of 8 oblong cells each with a size ranging from 32- 48 μm. Morphological observations using stereo- and SEM revealed the presence of non-glandular trichomes with cuticular warts and glandular peltate trichomes on the leaves of Mangifera indica. Transmission electron micrographs showed the presence of numerous mitochondria, starch grains, plastoglobuli, and plastids. The results for summer and winter leaves resembled somewhat similar-to-identical morphological characteristics on all fronts. For the phytochemical and biological assays, this study aimed to investigate some of the phytochemical and biological properties using different solvents (hexane, chloroform, and methanol) for extraction of the leaves of Mangifera indica for the summer and winter seasons. Preliminary phytochemical screening for the hexane, chloroform and methanolic extracts was done using a reflux extraction apparatus to uncover the presence of different metabolites and the anti-oxidant screening was done by the radical scavenging activity, which was established using the 2,2-diphenyl-1-picrylhydrazyl assay. Potent radical scavenging activity was exhibited for both summer and winter seasons with hexane and methanolic extracts for summer (IC50 of 19.53 μg/mL and 12.71 μg/mL respectively) and winter (22.32 μg/mL and 14.35 μg/mL respectively) in comparison to the control ascorbic acid which produced an IC50 of 3.20 μg/mL. The summer extracts had better radical scavenging IC50 capacity than winter extracts. The antibacterial activity of the methanolic leaf extracts for summer and winter of Mangifera indica were evaluated against the bacterial species: Gram-negative Escherichia coli (ATCC 25922) and Gram-positive: Staphylococcus aureus (ATCC ATCC 43300). For S. aureus (ATTC 43300), the summer crude extract displayed lower antibacterial activity than the control streptomycin, the summer extracts had a zone of inhibition of 14.17 mm while streptomycin had a 16.67 mm zone of inhibition. winter extracts had a zone of inhibition of 12 mm while streptomycin had a 13.67 mm zone of inhibition. For E. coli (ATCC 25922), the summer crude extract displayed higher antibacterial activity than the control gentamycin; the summer extract had a zone of inhibition of 18.05 mm while gentamycin had a 17.5 mm zone of inhibition. The winter extracts had a zone of inhibition of 8.5 mm. while gentamycin had a 14.5 mm zone of inhibition. Between seasons, summer had better antibacterial activity compared to winter for both Gram-positive and Gram-negative bacteria. Phytochemical screening showed the presence of phenols, flavonoids, tannins, and terpenoids, alkaloids, phytosterols, saponins, steroids, and carbohydrates. Potent radical scavenging activity was exhibited for the hexane and methanolic extracts for summer and winter, indicating that Mangifera indica is a potential source of medicinally important compounds. Antibacterial screening showed positive results with antibacterial properties for both summer and winter samples revealing its valuable biological activities. Summer overall performed better than the winter season. Future studies on this plant species are recommended to advance the use of indigenous herbal medicine or produce novel drug leads. To our knowledge, this study represents the first recent investigation in South Africa describing key foliar micromorphological features, phytochemicals, and biological activities of Mangifera indica L.
Phytochemical and pharmacological analyses of Embelia ruminata (E.Mey. ex A.DC.) Mez.
(2021) Rambaran, Neervana.; Naidoo, Yougasphree.; Baijnath, Himansu.
The discovery of novel phytoconstituents to treat a plethora of ailments has become urgent as the demand for phyto-resourced products has intensified. To complement the search for new phytoceutical products, the current dissertation propelled an investigation into the phytochemical and biological potential of a South African plant, Embelia ruminata (E.Mey. ex A.DC.) Mez. The vegetative structures (leaf and stem bark) and the reproductive organs (fruit and seed) of E. ruminata were sequentially extracted using hexane, chloroform and methanol. The subsequent phytochemical analyses, which included phytochemical tests, Fourier transform infrared (FTIR) and gas chromatography-mass spectroscopy (GC-MS) of the crude extracts revealed the presence of various pharmacologically bioactive compounds. Furthermore, the data from the radical scavenging investigations demonstrated that the methanolic seed and stem bark extracts (IC50 of 3.54 and 37.47 μg/mL, respectively) displayed potent scavenging activities compared with the standard butylated hydroxytoluene (IC50 of 91.09 μg/mL). Evidently, the radical scavenging results corroborated with the cytotoxic effects of the crude extracts, which indicated that the methanolic seed and stem bark extracts had strong anticancer activities against the cancer cell lines, i.e., breast cancer (MCF-7) and human lung cancer (A549). Additionally, silver nanoparticles (AgNPs) using the aqueous extracts of the leaf, stem bark and fruit of E. ruminata were synthesised and characterised by adopting a series of standard tests. The antibacterial potential of both the AgNPs and the crude extracts were evaluated and were distinctively more effective against the Gram-positive than the Gram-negative bacterial strains, with the AgNPs of fruit extracts synthesised at room temperature (23±2 °C) and the methanolic stem bark crude extracts showing the most promising activity. Two biomonitor strains, Chromobacterium subtsugae CV017 (short chain) and Chromobacterium violaceum ATCC 12472 (long chain), were used to test the quorum sensing (QS) violacein inhibition capacity of the respective extracts. Overall, the AgNPs and crude extracts displayed more effective QS inhibition against the long chain than the short chain biomonitor strain. Interestingly, the chloroform leaf, hexane and methanol seed extracts showed QS violacein inhibitory activities against both biomonitor strains, indicating the potential of these extracts against multiple bacterial strains. These findings provide evidence that E. ruminata is a possible source of potential medicinal compounds.
The secretory apparatus of Ceratotheca triloba (Pedaliaceae) : morphology and chemical composition of the secretion.
(2012) Karim, Taariq.; Naidoo, Yougasphree.; Naidoo, Gonasageran.
Ceratotheca triloba (Bernh.) E. Mey. ex Hook. f., commonly known as the wild foxglove, is a fast growing annual that is indigenous to southern Africa. The surface of the plant is covered with fine, hair-like trichomes, which exude sticky, aromatic substances. The plant is traditionally used to treat various abdominal ailments, insect infestation of the skin and leaf extracts are administered to induce abortion. In order to provide a scientific basis for the medicinal properties of C. triloba, this study was initiated to characterise the morphology and ultrastructure of the foliar trichomes and to determine the chemical composition of the secretion. Phytochemical tests and a range of microscopic techniques including stereo microscopy, scanning electron microscopy, transmission electron microscopy, histochemistry and fluorescence microscopy were used. Leaf surface imaging with stereo microscopy and SEM indicated the presence of two morphologically distinct glandular trichomes, capitate and peltate. The capitate trichomes are tall, consisting of a single basal cell, 2-4 stalk cells, a neck cell and a head that is made up of four secretory cells. Capitate trichomes of up to 14 stalk cells were observed on the abaxial side of flower petals. The peltate trichomes consisted of a basal cell, a single stalk cell and a multicellular head. The peltate trichome head generally consisted of four cells, but occasionally were seven or eight-celled. Fully developed trichomes were found to be concentrated on emergent leaves and probably serve protective function. The density of trichomes decreased as the leaf expanded. TEM showed that the secretory cells of peltate trichomes contained centralised nuclei and numerous peripheral vacuoles. Numerous mitochondria and ER cisternea were found throughout the cytoplasm. Osmiophilic plastids which were found near nuclei and golgi apparatus were in close proximity to the peripheral vacuoles. Similar observations were made for the stalk cells of both trichomes. The head cell of capitate trichomes however, contained large amounts of osmiophilic substances, ER cisternae and mitochondria. The head cells of peltate trichomes store the secretory product in vacuoles and secrete them upon cell rupture or cell dissolution. The secretory product of capitate trichomes is secreted through the cell membrane via an eccrine mode of secretion. Peltate and capitate trichomes appear to be secreting similar compounds, but the composition of each compound in the secretory material may vary between the trichomes. Histochemical and phytochemical tests reveal that the secretions are comprised of mucilage, phenolic compounds, lipids, flavonoids, tannins, saponins and fixed oils which may contribute to the medicinal properties of C. triloba. The observations made in this study provide useful information for additional research in the Pedaliaceae, and specifically in C. triloba. Future studies should isolate the active compounds for antimicrobial and antioxidant testing. Cytotoxicity testing should also be undertaken to test safety and efficacy of the active compounds.
Secretory structures of croton gratissimus Burch. Var. gratissimus (Euphorbiaceae): Micromorphology and Histophytochemistry.
(2018) Naidoo, Danesha.; Naidoo, Yougasphree.; Naidoo, Gonasageran.
Croton gratissimus Burch. variety (var.) gratissimus (Euphorbiaceae) has a widespread distribution in tropical Africa and is frequently used in African traditional medicine to treat various ailments. In South Africa, dried leaves of C. gratissimus are smoked to treat influenza, colds and fever. Due to its extensive use in traditional medicine, research on the phytochemical composition of C. gratissimus has been documented. According to literature, these phytochemicals are possibly secreted or accumulated in secretory structures. However, little or no research is available on the structures involved in the production and/or accumulation of phytochemicals in C. gratissimus. Therefore, this study aimed to describe the micromorphology of trichomes and laticifers from the leaves and stems of C. gratissimus as well as to identify the possible site of synthesis of phytochemicals. Furthermore, the chemical composition and antibacterial properties of phytochemicals in the leaves and stems were also determined. In addition, the antibacterial activity of biosynthesised silver nanoparticles (AgNPs) from leaf and stem crude extracts was also investigated. Microscopic investigations revealed the presence of lepidote and glandular trichomes, and non-articulated unbranched laticifers on/in the leaves and stems of C. gratissimus. The lepidote trichomes formed a dense indumentum over the abaxial surface of leaves throughout all developmental stages, canopying the underlying glandular trichomes. Laticifers were present in the leaves and stems and were predominantly associated with the vascular tissue in both organs. All structures stained positive for alkaloids, phenolic compounds and lipids with histochemical tests. Phytochemical analyses of the leaves and stems revealed alkaloids, amino acids, phenolic compounds, flavonoids, carbohydrates, terpenoids, saponins and fixed oils and fats in both leaf and stem extracts. The methanolic leaf and stem extracts demonstrated weak to strong activities against various bacteria strains, which are attributed to the several bioactive compounds identified from Gas Chromatography-Mass Spectrometry (GC-MS) analyses. In addition, AgNPs were successfully biosynthesised from the methanolic leaf and stem extracts. Particles synthesised from both extracts were spherical in shape, but their size distribution differed between organs. Antibacterial assays demonstrated a stronger activity of particles from leaf extracts compared to those from stems. These findings corroborate the use of C. gratissimus in traditional medicine and indicate that various structures are involved in the production of bioactive compounds which contribute to the medicinal properties of this plant. Furthermore, the antibacterial activities exhibited by the extracts and AgNPs suggest that C. gratissimus is a potential source of antibacterial agents.
Structure, biology and chemistry of plumbago auriculata (plumbaginaceae).
(2017) Singh, Karishma.; Naidoo, Yougasphree.; Baijnath, Himansu.
Plumbago auriculata Lam. is endemic to South Africa and is often cultivated for its ornamental and medicinal uses throughout the world. Belonging to the family Plumbaginaceae this species contains specialized secretory structures on the leaves and calyces. This study focused on the micromorphological, chemical and biological aspects of the species. Micromorphological studies revealed the presence of salt glands on the adaxial and abaxial surface of leaves and two types of trichomes on the calyces. “Transefer cells” were reported for the first time in the genus. The secretory process of the salt glands was further enhanced by the presence of mitochondria, ribosomes, vacuoles, dictyosomes and rough endoplasmic reticulum cisternae. Histochemical and phytochemical studies revealed the presence of important secondary metabolites that possess many medicinal properties which were further analyzed by Gas chromatography-mass spectrometry (GC-MC) identifying the composition of compounds in the leaf and calyx extracts. A novel attempt at synthesizing silver nanoparticles proved leaf and calyx extracts to be efficient reducing and capping agents that further displayed good antibacterial activity against gram-positive and gram-negative bacteria. Biological studies revealed for the first time the presence of three variants of flower colour (white, pale blue and deep blue) and each colour had a characteristic sex-morph described as “Pin” or “Thrum.” Due to the “Pin” and “Thrum” scenario, plants are reported to be self-incompatible. However, the findings of this study suggested that plants were also self-compatibile. Graphical demonstration of calyx trichomes showed their involvement in insect entrapment often resulting in the death of the insect due to the struggle to free itself. This study concludes that P. auriculata is of good medicinal value and can contribute towards drug development and other medicinal uses in traditional markets as well as in the cosmetic and pharmacological industries. This species has striking morphological and biological features and possesses good value for future perspectives.
A systematic study of the genus rhoicissus planch, (vitaceae) in KwaZulu-Natal.
(2015) Kunene, Sinethemba Faith.; Nicholas, Ashley.; Naidoo, Yougasphree.; Boon, Richard Graham Campbell.
The family Vitaceae, sometimes referred to as the grape family, comprises about 700 to 800 species and 13 to 14 genera, which includes Rhoicissus Planch. Rhoicissus contains 12 species all of which are described as climbing shrubs with tendrils that are without adhesive discs. This study was aimed at updating the taxonomy of the genus Rhoicissus in KwaZulu-Natal such that the names and number of species contained within the genus reflect the current findings. This dissertation looks primarily at the taxonomy of the leaves of the Rhocissus species of KwaZulu-Natal. The reason for this is that this work is meant to help conservationists, environmental managers, rangers, amateur botanists and others who will usually only encounters these species in their vegetative state. It is at this audience that this dissertation is aimed. Rhoicissus tridentata was found to be a complex that is made up of three subspecies: R. tridentata subsp. cuneifolia; R. tridentata subsp. diplonervia and R. tridentata subsp. tridentata. Phenetic results, scatter plots and polygonal graphs did not all support the division of R. digitata into three subspecies. Morphological results, however, did show the slight differences between the subspecies of R. digitata which are R. digitata subsp. digitata; R. digitata subsp. oravivens and R. digitata subsp. emarginata. The other species of Rhoicissus (R. revoilii; R. rhomboidea; R. sessilifolia and R. tomentosa) were all found to be distinct species.
The secretory scales and medicinal properties of combretum erythrophyllum.
(2021) Bantho, Sahejna.; Naidoo, Yougasphree.; Yaser, Hassan Dewir.; Singh, Moganavelli.
Medicinal plants are known to contain phytometabolites that could effectively improve an individual’s state of health. Species of Combretum are highly valued in Africa due to the plethora of their traditional medicinal uses. Combretum erythrophyllum. Burch. Sond., commonly known as the river bushwillow, is known to contain medicinally important phytometabolites. Traditionally, the foliage is used to treat venereal diseases and abdominal pain, whilst the bark is used to alleviate sores, infertility, and labour pains. Although C. erythrophyllum has numerous traditional medicinal uses, there is limited scientific knowledge on the micromorphological structures and the associated exudate. Thus, this study aimed to characterize the micromorphological features of leaf and stembark secretory apparatus of C. erythrophyllum, using light and electron microscopy. Furthermore, a histo-phytochemical analysis was conducted to determine the presence and localization of phytometabolites within the trichomes and exudate. The antioxidant, antibacterial, apoptotic and cytotoxic potential of the leaf and stembark extracts were also evaluated. The micromorphological analysis identified the presence of peltate scales and non- glandular trichomes across surfaces. Peltate scales were comprised of a sunken basal cell, bicellular stalk, and a multicellular head. Head cell count appeared to increase upon leaf maturation. The granulocrine pathway was identified as a possible mode of secretion for C. erythrophyllum due to the extensive presence of vesicles, vacuoles, and electron dense material within the peltate scales. Preliminary histo-phytochemical analyses revealed the presence of carbohydrates, sterols, lipids, phenolic compounds, total proteins, alkaloids, and essential oils. Thin-layer chromatography allowed for the visualization of 36 compound classes while gas chromatography-mass spectrometry showed 266 compounds present. Fourier-transform infrared spectroscopy analysis confirmed the presence of phenols, alkenes, amines, alcohols, and esters among many. The antioxidant ability of the generated extracts were evaluated using the 2,2- diphenyl-1-picryl-hydrazyl-hydrate antioxidant assay and Ferric Reducing Antioxidant Power assay. A positive correlation between % inhibition and extract concentrations, was noted in both. In both instances, the methanol stembark extracts performed the best, (Leaf- 5,2866 and Stembark- 4,2866 µg/mL). Furthermore, the results obtained from the total flavonoid assay correlated with the trend observed through the total phenolic assay, whereby methanolic extracts yielded most promising results. Additionally, this study aimed to generate silver nanoparticles using crude extracts. A novel protocol for the synthesis of silver nanoparticles (AgNPs) using the leaf and stembark extracts of C. erythrophyllum was established. The generated AgNPs were characterized and evaluated for its potential antibacterial activity. Methanolic extracts inhibited the growth of Pseudomonas aeruginosa, Bacillus subtilis, Methicillin Resistant Staphylococcus aureus, and Staphylococcus aureus. Lastly, the generated crude extracts displayed promising results when evaluated for their cytotoxic and apoptotic abilities however upon nano- vii encapsulation the cytotoxic and apoptotic capabilities increased significantly. In correlation with the above, the AgNPs appeared to intensify the overall inhibition activity. Based on the findings of the study, Combretum erythrophyllum has a reservoir of unexplored allopathic potential which could revolutionize the medicinal world.