Biological Sciences

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An investigation of the prerequisite conditions which enable invasion of moist grasslands by Dalbergia obovata.
(2019) Stewart, Terry.; Scogings, Peter Frank.; Baijnath, Himansu.
Encroachment by Dalbergia obovata into moist coastal grasslands within eThekwini Municipality was identified as a potential threat to the conservation of this threatened habitat type. An investigation was undertaken to confirmation whether or not D. obovata was in fact encroaching into the city's grasslands and to identify the probable underlying drivers and local factors that contributed to encroachment. The investigation comprised four areas of focus. The first was an assessment of the management practices and records of D. obovata encroachment extracted from the available reserve management records of seventeen nature reserves and conservation areas. The summarised data from the records was then processed using a Chi-square test and Principal Components Analysis. The second phase focussed on the application of field surveys to record the distribution patterns of D. obovata within four selected management areas. The results were then captured in a GIS map against which the results of the Chi-square and PCA tests were compared. In phase three a simple theoretical ballistics model was developed from experimental data to predict the anomochoric distribution of D. obovata diaspores from the forest into adjacent grasslands and the critical positioning of parent plants in the host trees in relation to the edge of the canopy. The final focal area involved the mapping of individual plants within stands of D. obovata and comparison against sixteen years of historical orthophoto records in order to determine the historic patterns and rates at which D. obovata became established and propagated within the grasslands. During this part of the investigation the vegetative propagation of D. obovata by clonal propagation from lateral branches and roots was identified and which provided an explanation of how D. obovata was able to form large dense stands with no evidence of canopy contact mortality. The final conclusions were that D. obovata parent plants had to be positioned on the edge of the forest canopy for diaspores to successfully escape the canopy, that successful establishment of D. obovata in grasslands from any particular parent plant was infrequent and that D. obovata did not become established in the presence of large mixed feeder herbivores. However once established in the grasslands, the ability to spread via clonal propagation enabled D. obovata to both outcompete grass species for available resources and be resilient to conventional bush encroachment management practices which relied on controlled burning programs.
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.
Structural, chemical and physiological investigations of bilirubin found in seed arils of strelitzia nicolai.
(2017) Dwarka, Depika.; Baijnath, Himansu.; Thaver, Veneesha.; Naidu, Mickey.
In 2009, a team of researchers from the Florida International U niversity discovered bilirubin which is an animal compound in the se ed arils of Strelitzia nicolai , commonly known as the White Bird of Paradise plant. Bilirubin is an endogenous yellowish compound that is formed following the standard catabolic pathway by the breakdown of haem. This catabolism is an essential practice in the human body as it allows for the elimination of waste products. Bilirubin is formed in humans some vertebrates and invertebrates. Previously thought to be a toxic compound if accumulated, recent ad vancements in medical sciences show bilirubin as an eff ective antioxidant. This study describes novel protocols to reveal new insights into the presence of the only animal pigment found in S. nicolai arils, the potential advantages of bilirubin found in a plant and its therapeutic value indications. In vitro a nd in vivo experim ents using the aril extract was conducted in order to assess the antioxidant , anti cancer and toxicity dosage of S. nicolai aril extract. In vitro studies showed that S. nicolai aril extract caused apoptosis in 52% of Hela cancer cell lin es. These results indicate that S. nicolai aril s extract possess conceivable chemo preventive properties. In vivo results in a rat model showe d no acute toxicity nonetheless, t hese results were inconclusive as a lengthier chronic study needs to be conducte d in order to completely rule out toxicity. An ultrastructure study of the seed arils was embarked in order to integrate supplementary knowledge The developing seeds were grouped in five stages according to seed maturity and aril colour. The arils were an alysed using light and electron microscopy. The Hall’s staining which is generally used on human tissue was modified to detect bilirubin on the surface of the aril tissue. Light microscopic results showed that as the aril matures it undergoes an atypical c olour change from opaque to yellow and finally a deep orange. This colour change might be attributed to the accumulation of bilirubin in the aril tissue. This hypothesis was further justified by cryo SEM and TEM which shows the trend of an accretion of a p igment as the aril matures. In addition, the inclination of aril maturity in S. nicolai follows an analogous prototypical pathway to that of bilirubin catabolism in humans. This study consequently highlights the potential use of S. nicolai aril extract co ntaining bilirubin and also attempts to relate aril structure with impending function.
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.

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Browsing Biological Sciences by Author "Baijnath, Himansu."