Browsing by Author "Koorbanally, Neil Anthony."

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A phytochemical and elemental analysis of senecio serratuloides DC, and its antidiabetic potential.
(2024) Gumede, Andile.; Koorbanally, Neil Anthony.; Moodley, Roshila.; Mshengu, Bongiwe Pridesworth.
Senecio serratuloides DC, from the Asteraceae, has been widely used in South African traditional medicine for the treatment of various conditions such as swollen gums, chest pains, sores, cuts, burns and ulcers. This study was conducted to determine a chemical profile of the plant, both in terms of the secondary metabolites and essential and toxic elements contained in the plant. The plant extracts were further tested for their antibacterial (minimal inhibitory concentrations) and antidiabetic potential (α-amylase and α-glucosidase inhibitory activity). The phytochemical analysis of the leaves and stems resulted in the isolation of the sterols, β- sitosterol (S1) from the stems, and stigmasterol (S2) and stigmasterol glucoside (S3) from the leaves. A further rare sterol, 18α-ursa-12,20(30)-dien-3β-ol (S4) was also isolated from the leaves. Three flavonoids, quercetin (S5), quercetin-3-O-glucoside (S6) and hesperidine (S7) were also isolated from the leaves, along with an aromatic acid, caffeic acid (S8). Extracts of the plant showed good in vitro antidiabetic activity, with the methanol extract from the leaves exhibiting the highest activity against α-glucosidase and α-amylase. However, the extracts did not exhibit any significant antibacterial activity in the assays carried out. The elemental analysis of the plant indicated a decreasing order of Ca > Mg > Zn > Fe > Co > Cu > Cr > Mn > Ni > As > Se. The leaves also showed good quantities of vitamin C, with an appreciable amount being extracted during the cooking phase. The results also show that moderate consumption of the leaves pose no probable threats of metal poisoning. The extracts obtained from S. serratuloides DC were found to have no antibacterial activity. This is surprising, since some of the isolated compounds were reported to have shown some antibacterial properties, however, these may have been too low to have any significant effect in the crude extracts.
Extractives from eucomis montana and agapanthus inapertus.
(2003) Pillay, Bavani.; Mulholland, Dulcie Aca.; Koorbanally, Neil Anthony.
Two species belonging to different families were investigated, Eucomis montana from the Hyacinthaceae and Agapanthus inapertus from the Agapanthaceae. To date no previous chemical investigation on Eucomis montana has been reported. Eucomis species are routinely harvested, processed and sold for the treatment of various ailments ranging from toothache, gastro-intestinal ailments, pain-producing ailments and venereal and urinary diseases. Members of the genus have shown to contain steroidal compounds and homoisoflavonoids. In this work one nortriterpenoid, a eucosterol type derivative and eleven homoisoflavonoids belonging to four classes, the 3-benzyl-4-chromanone, the 3-benzyl-3-hydroxy-4-chromanone, the 3-benzylidenyl-4-chromanone and the scillascillin type were found in the bulbs of Eucomis montana. Agapanthus species are also used by a number of African tribes medicinally. The bulbs and rhizomes of this family have been reported to contain steroidal saponins and sapogenins. In this work the roots of Agapanthus inapertus have been investigated and a tignan precursor and a lignan have been found. Structures of the compounds isolated were determined using spectroscopic techniques.
The extractives from Sophora velutina and Calpurnia aurea and their biological activity.
(2012) Korir, Erick Kipkoech.; Koorbanally, Neil Anthony.
This work is an account of the phytochemistry and biological activity of two related plant species within the plant family the Fabaceae, Sophora velutina from the subtribe Sophoreae and Calpurnia aurea of the subtribe Podalyrieae. Members of this family are known to contain quinolizidine alkaloids and flavonoids, which are chemotaxonomic markers in the Fabaceae. The phytochemical investigation of Sophora velutina resulted in the isolation of ten compounds, including five novel quinolizidine alkaloids, N-methylenehydroxycytisine (A-1), 7- hydroxylupanine (A-2), 6,7-dihydroxylupanine (A-3) and 17-oxo-thermopsine (A-4) from the fruits and velutinine (A-5) from the bark along with the known quinolizidine alkaloids Nmethylcytisine (A-6) and cytisine (A-7), and a cinnamate ester, methyl-3-(3',4'- dimethoxyphenyl)-2-propenoate (A-8) and triterpenoids lup-20(29)-ene-3β-ol (A-9) and 12- oleanen-3-one (A-10). The isolated compounds were tested for their antibacterial activity against Enterococcus faecalis and Pseudomonas aeruginosa. P. aeruginosa showed resistance against eight of the ten samples tested with only the cinnamate ester and the steroid 12-oleanen- 3-one (A-10) being slightly active at 200 and 175 μg mL-1, respectively. However, the quinolizidine alkaloid, N-methylcytisine (A-6) and 12-oleanen-3-one (A-10) showed good antibacterial activity against E. faecalis, with MIC values of 20.8 and 10.9 μg mL-1, respectively, with 17-oxo-thermopsine (A-4), another quinolizidine alkaloid, and the cinnamate ester showing moderate antibacterial activity against E. faecalis at concentrations of 125 μg mL-1 and 100 μg mL-1, respectively. Calpurnia aurea yielded five isoflavones, 4′,5,7-trihydroxyisoflavone (B-1), 7,3′-dihydroxy-5′- methoxyisoflavone (B-2), 7-hydroxy-4′,8-dimethoxyisoflavone (B-3), 7-acetoxy-4′,8- dimethoxyisoflavone (B-4) and 3',7-dihydroxy-4′,8-dimethoxyisoflavone (B-5), a pterocarpan (3- acetoxy-9-methoxypterocarpan) (B-6) and a quinolizidine alkaloid (calpurnine) (B-7) all of which were isolated from the stem and bark. These isoflavones were screened for in vitro anticancer activity against breast (MCF7), renal (TK10) and melanoma (UACC62) human cell lines, where 3',7-dihydroxy-4′,8-dimethoxyisoflavone (B-5) was found to be the most active amongst all the compounds tested, followed by 3',7-dihydroxy-5'-methoxyisoflavone (B-2), also with a hydroxyl and methoxy group on the phenyl ring but in the 3' and 5' positions, respectively. Elucidation of the compounds was done mainly by 1D and 2D NMR spectroscopy together with mass spectrometry, infrared, and ultraviolet spectroscopy. Antibacterial and anticancer assays were carried out using standard assays at the Centre for Scientific and Industrial Research (CSIR), Pretoria, South Africa.
Extractives from the amaryllidacea and the fabaceae.
(1999) Koorbanally, Neil Anthony.; Mulholland, Dulcie Aca.; Crouch, Neil Robert.
This work is an account of investigations into the chemistry of one of the members of the Amaryllidacae family, Ammocharis coranica, and one of the members of the Fabaceae family, Sophora velutina. Chapter one is an account of the extractives from the bulbs of Ammocharis coranica. In all, twelve compounds, eight alkaloids and four cycloartane compounds have been isolated of which one alkaloid and one cycloartane compound have not been described previously. Plants belonging to the Amaryllidacae family have been used by traditional healers, especially in Africa, to treat a range of illnesses and diseases. The alkaloids isolated from these plants have been shown to exhibit responses to muscle stimulant, antiviral, antifungal, antiyeast, antimalarial, cytotoxic and antitumoural activities. Ammocharis coranica is used by the Zulu tribe in South Africa to treat any illness believed to be caused by witchcraft. Alkaloids from the three most common types among the isoquinoline group were found in this species. These are lycorine, 1-O-acetyllycorine, hippadine, acetylcaranine, and the novel 1-O- acetyl-9-norpluviine from the lycorine type, 6-α-hydroxypowelline from the crinine type and hamayne and crinamine from the haemanthamine type. Cycloartane compounds have not been reported previously from the Amaryllidaceae family. All four cycloartane compounds had a common side chain, containing an olefinic methylene group at position 24, but differed in their substituents at positions 3 and 4. These compounds were found to be 24-methylenecycloartan-3β-ol, cycloeucalenol, cycloeucalenone and the novel compound 4-methylenepollinastanone. Chapter two is an account of the extractives from the seeds of Sophora velutina. The seeds of other Sophora species have been used in traditional ceremonies by the Indians of the Southwest United States and adjacent Mexico because of their hallucinogenic activity. The seeds of Sophora velutina subsp. zimbabweensis found in Zimbabwe are suspected to have historically been used by the natives for their hallucinogenic properties. These plants have been known to contain several quinolizidine alkaloids, flavonoids and isoflavonoids. One alkaloid, N-methylcytisine and two isoflavones, pseudobaptigenin and calycosin, as well as the common phytosterol, β-sitosterol were isolated from the seeds of this species. N-methylcytisine is a common quinolizidine alkaloid, isolated previously from several Sophora species and pseudobaptigenin and calycosin are well known isoflavones, isolated previously from several species in the Fabaceae.
Extractives from the ptaeroxylaceae and the mesembryanthemaceae.
(2001) Koorbanally, Neil Anthony.; Mulholland, Dulcie Aca.
This work is an account of the investigations into the chemistry of two Cedrelopsis species from the Ptaeroxylaceae, Cedrelopsis grevei and Cedrelopsis microfoliata and a species from the Mesembryanthemaceae, Khadia alticola, as well as investigations into the synthesis of hydroxylated and prenylated chalcones. Cedrelopsis grevei, commonly called Katrafay, is amongst the many medicinal plants of Madagascar, being used to relieve muscle fatigue when the bark is soaked in hot water. Previous investigations of the wood and stem bark of this plant, have yielded chromones and coumarins and a recent investigation of the stem bark of a specimen collected in the north of Madagascar has yielded two novel limonoids of unusual structure, cedmilinol and cedmiline. The fruit and seed of Cedrelopsis grevei have not been studied previously and a phytochemical investigation of these plant parts was undertaken in this work. The dichloromethane extract of the fruit and seeds yielded, after column chromatography, a dihydrochalcone, uvangoletin, a flavanone, 5,7dimethoxypinocembrin, two simple chalcones, cardamonin and flavokawin Band three prenylated chalcones, 2’-methoxyhelikrausichalcone, cedreprenone and cedrediprenone. Three of these compounds, 2’-methoxyhelikrausichalcone, cedreprenone and cedrediprenone have not been isolated previously. Cedrelopsis microfoliata is another medicinal plant used in Madagascar. The leaves of this plant are used to prepare a decoction for woman to drink after childbirth. This is the first phytochemical investigation of Cedrelopsis microfoliata. The hexane extract of the dried stem bark yielded three compounds after column chromatography, a chalcone, microfolian and two flavanones, microfolione and (+)-agrandol. The dicholoromethane extract of this compound yielded four compounds after column chromatography, three coumarins, cedrecoumarin A, obliquin and microfolicoumarin and a sesquiterpenoid, sesquichamaenol. Four of the compounds isolated from Cedrelopsis microfoliata, microfolidione, microfolione, (+)-agrandol and microfolicoumarin have not been isolated previously. Khadia alticola is one of the species added to "Khadi", a Tswana/South Sotho name for beer brewed traditionally using the fleshy roots of a variety of taxa. Khadia is also reported to be used medicinally by the Manyika people of the Umtali district of Zimbabwe. The phytochemical investigation of the roots of Khadia alticola, which have not been studied previously, was undertaken to determine whether mesembrine type alkaloids were present in this species and thus contributing to the "potency" of the beer brewed traditionally. No mesembrine alkaloids were isolated in this work, however, a common sterol, sitosterol was isolated from the acidic chloroform fraction of the roots of this species and a flavonoid, 3,4',5,7-tetrahydroxyflavan was isolated from the basic chloroform fraction. Two chalcones, 3’,5’-dihydroxychalcone and 2’-hydroxychalcone were synthesised using the Claisen condensation. An isoprenylated acetophenone intermediate and an isoprenylated chalcone were also synthesised.
Imidazolium, phosphonium and pyridinium ionic liquids with flourinated anions : synthesis characterization and applications.
(2013) Ibrahim, Hamisu.; Koorbanally, Neil Anthony.
Four sets of ionic compounds were synthesized, each with an organic spacer between two ligands creating a dication with the bromide as the counter anion. In each of the sets of ionic compounds, the counter anion was exchanged in a metathesis reaction with either all or some of NaBF4, KPF6, CF3SO3Li and CF3COONa in an effort to produce fluorinated ionic liquids. The first set of ionic salts was based on the reaction between 1-methylimidazole and a,a– dibromo-p-xylene to form a bis(methylimidazolium) cation with an aromatic spacer between them. This was followed by metathesis reactions with four fluorinated anion sources, which yielded new fluorinated imidazolium salts [C6H4(CH2(C4H6N2)2]2+ 2[A]- where A = BF4 (A- 2), PF6 (A-3), CF3SO3 (A-4) and CF3COO (A-5). The compounds were characterized by 1H-, 13C-, 19F-, 31P-NMR and IR spectroscopy. Single crystal X-ray diffraction data of compounds A-2, A-3 and A-4 were carried out where the study revealed that the different fluorinated anions affected the spacial arrangement of atoms and the extent of cation-anion interactions and hence, influenced the stability and coordination properties of the imidazolium salts. A trend was observed which related the strength of cation-anion interaction to physical properties such as melting point. A further set of ionic salts, keeping the same organic moiety, the a,a-dibromo-p-xylene but this time changing the ligand to that of triphenylphosphine (PPh3) was synthesized to first produce the dibromide (B-1) and then the fluorinated salts B2-B5 with CF3SO3Li, NaBF4, KPF6 and CF3COONa respectively. Compounds B2-B5 were all novel compounds whose synthesis have not been reported previously. The salts were characterized by 1H, 13C, 19F, 31P NMR, and IR spectroscopy. The organic salts were tested for their antimicrobial activity and showed significant activity against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Salmonella typhi, Candida albicans, and Streptococcus pyogenes when compared with the activities of the standard antimicrobial chloramphenicol and antifungal nystatin. The crystal structure of B-3, the ditetrafluoroborate is also discussed. In the third set of ionic salts, the solvent free reaction of 1-methylimidazole and alkyl dibromides (RBr2; R = -CH2-, -(CH2)3-, -(CH2)4-, and -(CH2)5-), were synthesized (C1a-4a) in a highly exothermic reaction. This was followed by metathesis reactions with fluorinated anion sources, NaBF4 and KPF6 to produce the fluorinated imidazolium ionic compounds C1b-4b and C1c-4c respectively. All twelve compounds were characterized by 1H-, 13C-, 19F-,31P-NMR, and IR spectroscopy. A trend was observed relating the length of the alkyl chain in the cations and the strength of cation-anion interactions to the melting point of the compounds. The dibromide ionic compounds decreased in melting point as the length of the alkyl spacers increased. The strength of the cation-anion interactions were strongest for the Br- ionic liquids followed by the PF6 - and the BF4 - counteranions as demonstrated by their melting points which increased in the order of M(BF4)2 < M(PF6)2 < MBr2. NMR studies of the synthesised ionic salts were also carried out to determine how the shifts of the alkyl groups and ligands changed as the anion changed. In the last set of compounds, pyridine was explored as the ligand with p- , -dibromoxylene and 1,1-dibromomethane respectively to yield the quarternized salts D1a and D2a respectively, followed by metathesis reactions with the fluorinated anion sources, NaBF4 and KPF6 to produce fluorinated pyridinium ionic liquids D1b-c and D2b-c. Compounds D1b and D2c are novel compounds as the combination of cation and anion had not been synthesised previously. The synthesis of D2a was carried out without the use of solvents and the metathesis reactions carried out with ethanol and water and can be considered as green reactions. 2D NMR studies of the synthesised compounds are reported here.
The isolation, structure elucidation and biological testing of compounds from Plectranthus hadiensis.
(2010) Dukhea, Shiksha.; Koorbanally, Neil Anthony.; Moodley, Brenda.
Three diterpenes of the abietane class, 7b-acetoxy-6b-hydroxyroyleanone (I), 6b,7b- dihydroxyroyleanone (II) and ent-pimara-8(14),15-diene-3b,11a-diol (III) and three triterpenes, 2a,3a,19 -trihydroxyurs-12-en-28-oic acid (IV), stigmasterol (V) and lupeol (VI) were isolated from the stem and leaf material of Plectranthus hadiensis. The structures of the compounds were elucidated using 2D NMR spectroscopy and Mass spectrometry. All six compounds have been isolated previously, but this is the first occurrence of compounds III-VI in Plectranthus hadiensis. This is also the first report of the isolation of a pimarene from Plectranthus, which provides a biochemical link to other genera in the family Lamiaceae where this class of compounds exist. Compounds I to IV were tested for their antibacterial activity against Enterococcus faecalis and Pseudomonas aeruginosa as well as their anticancer activity against breast (MCF-7), renal (TK- 10) and melanoma (UACC-62) cell lines. Compounds I and II exhibited good antibacterial activity against Enterococcus faecalis and Pseudomonas aeruginosa and although the entpimara- 8(14),15-diene-3 ,11 -diol (III), was inactive against E. faecalis, it was very active against P. aeruginosa. Compound IV, the triterpenoid, was structurally different to I-III and did not show any anti-bacterial activity. Compounds I-III were weakly active toward the cancerous renal (TK-10), melanoma (UACC-62) and breast (MCF-7) cell lines, while IV was inactive in all of the cell lines.
Metal catalysed cross-coupling reactions of nitrogen and fluorine containing heterocyclic compounds.
(2016) Alapour, Saba.; Koorbanally, Neil Anthony.
Abstract available in PDF file.
Oxidative degradation of textile dyes with hypochlorite and chlorine dioxide.
(2010) Nadupalli, Srinivasu.; Jonnalagadda, Sreekantha Babu.; Koorbanally, Neil Anthony.
The oxidation reaction mechanisms of water soluble textile dyes amaranth (an azo dye), brilliant blue-R (a triaryl dye) and safranine-O (an azine dye) with oxidants- hypochlorite and chlorine dioxide, were investigated. The detailed kinetics of the reactions of the three dyes was studied under excess concentrations of the oxidant and other reagents. The depletion of concentration of the chosen dye, taken at low concentration was monitored using a Hi-Tech SF-61 DX2 double mixing micro volume stopped-flow apparatus. The hypochlorite initiated oxidations were investigated as function of varying concentration of oxidant and hydrogen ion, ionic strength and temperature. For the chosen dyes and reaction conditions, the depletion of dye followed pseudo first-order kinetics and the rate constants were estimated using KinetAsystTM software. All the three reactions had first-order dependence on the oxidant concentration, and the reaction rates increased by varied extent with increase in [H+]0. The role of acid in their reaction mechanisms was established. The kinetic data was analysed to evaluate the rate constants for the competitive pathways initiated by hypochlorite ion and hypochlorous acid. The overall second-order rate coefficients for the OCl- and HOCl initiated reactions were estimated for all the three reactions. Major oxidation products for the reactions were separated and characterized by 1H NMR and 13C NMR and GC-MS techniques and the stoichiometry was established. The energy parameters inclusive of Arrhenius factor, enthalpy, entropy and energy of activations for the oxidation of three dyes both by OCl- and HOCl species were estimated. Based on the experimental findings, the probable rate laws, mechanisms and reaction schemes were described. Simulations studies were conducted to validate the proposed mechanisms using SIMKINE2 computer programme. The rate of oxidation of safranine-O is greater than that of amaranth and brilliant blue-R with OCl- / HOCl reaction. Following similar protocol, the oxidations of the chosen dyes with chlorine dioxide were investigated by monitoring the depletion kinetics of dye as function of varying concentration of ClO2 and OH- ion, ionic strength and temperature. All the three dyes, exhibited pseudo first-order kinetics and the rate constants were estimated using KinetAsystTM software. All the three reactions had first-order dependence on the oxidant concentration at pH conditions 7.0, 8.0 and 9.0 suggesting that reaction mechanism remains unaltered with pH variation. The effect of hydroxide ion on the reaction rate revealed that it acts as catalyst. All the three reactions had first-order dependence on [OH-]0, when its concentration was low; but the order with respect to [OH-] decreased as [OH-] increased stoichiometry proportion to reactants. The catalytic constant for hydroxide catalysed reaction was estimated for all the three reactions. Kinetic salt effect experiments were conducted to identify the possible reaction species involved in the reactions. The major reaction products were characterized by 1H NMR, 13C NMR and GC-MS techniques. The stoichiometry ratios were established and energy parameters were estimated. The rate laws and probable reaction mechanisms were proposed and appropriate reaction schemes for all the reactions were described. The elucidated mechanisms were confirmed by simulation studies using SIMKINE2 software. At neutral pH the rate of oxidation of amaranth is greater than safranine-O and brilliant blue-R, and brilliant blue R being the slowest.
Phytochemical analyses and biological activities of four South African ficus species (moraceae)
(2015) Awolola, Gbonjubola Victoria.; Koorbanally, Neil Anthony.
Abstract available in PDF file.
Phytochemical and analytical studies on two indigenous medicinal plants found in KwaZulu-Natal : Carissa macrocarpa and Harpephyllum caffrum.
(2012) Moodley, Roshila.; Jonnalagadda, Sreekantha Babu.; Koorbanally, Neil Anthony.
Vulnerable communities and rural households usually turn to natural resources for their nutritional and healthcare needs. However, very little is known about the nutritional and medicinal value of many plant species utilized by these communities despite widespread scientific research on medicinal plants. This is mainly due to the huge numbers of medicinal plants that are in use. This study aimed at investigating two plants species that are indigenous to KwaZulu-Natal and contain edible fruits namely Carissa macrocarpa and Harpephyllum caffrum, as a source of secondary metabolites and essential dietary elements, because of their claimed medicinal value and nutritional potential. The analytical results indicate that the fruits are a good source of essentiary dietary elements and can contribute to the recommended dietary allowances (RDAs) for most nutrients. Phytochemical analysis shows that the fruits of C. macrocarpa are rich in the pharmacologically active pentacyclic triterpenoids whose immune boosting properties are well-known. The fruits can therefore be consumed to boost the immune system in areas where immune boosting supplements are out of reach. The fruits of H. caffrum were found to be rich in the flavan- 3-ol antioxidant, (+)-catechin. The fruits can therefore be used as a substitute for antioxidant supplements taken in Western and European countries. This study lends scientific credence and validity to the ethnomedicinal use of these plants and reveals the nutritional and medicinal benefits of consuming the indigenous edible fruits. It also adds to the growing body of research on indigenous medicinal plants.
Phytochemical and anti-drepanocytosis studies of Cajanus cajan, Callistemon viminalis, Melaleuca bracteata var. Revolution Gold and Syzygium guineense.
(2010) Tshibangu, Damien Sha-Tshibey.; Shode, Francis Oluwole.; Koorbanally, Neil Anthony.
All over Africa, traditional healers use medicinal plants to prepare medicines to treat a wide range of illnesses. One of these illnesses is sickle cell anaemia or drepanocytosis or sicklemia. This disease is particularly common among sub-Saharan Africans with a clear predominance in equatorial Africa. However, it also exists in North Africa, Greece, Turkey, Saudi Arabia and India. An estimated 50 million people are affected worldwide. A literature review on sickle cell anaemia revealed that a number of plants have anti-drepanocytosic activity. The availability and frequency of ethnobotanic use of plants were taken into account when selecting the plants investigated in this study. Cajanus cajan, Callistemon viminalis, Melaleuca bracteata var. Revolution Gold and Syzygium guineense (from DRC and South Africa) were selected for study. The selected plants were subjected to modern phytochemical analysis. A total of 8 compounds were isolated from the plants’ extracts and their structures determined by modern spectroscopic techniques (1D and 2D NMR, FT-IR and MS). S. guineense from DRC (Democratic Republic of Congo) yielded flavanonoid glycoside (A) as its major chemical constituent. The South African S. guineense afforded 4 compounds namely betulinic acid (B), sitosterol (C), friedelan-3-one (D) and a betulinic acid derivative (E). Cajanus cajan showed the presence of fatty acids, one of them was characterized as an unsaturated fatty acid (I). Callistemon viminalis afforded one compound, betulic acid (F) and Melaleuca bracteata afforded two compounds which were characterized as betulinic acid acetate (G) and ursolic acid acetate (H). CH3-(CH2)n-CH2-CH=CH-CH2-CH=CH-(CH2)n-CH2-CH2-COOH The investigation of the anti-drepanocytosis activities of the extractives and their crude extracts showed in vitro antisickling activity. Ethyl acetate crude extracts of Callistemon viminalis and Melaleuca bracteata; hexane, dichloromethane and ethyl acetate crude extracts of Syzygium guineense of DRC, betulinic acid, betulinic acid acetate and maslinic acid showed a high antisickling activity, more than 70% of normalization. The compound BF4, a fatty acid, from Melaleuca bracteata was found to have a medium activity, between 50 and 70% of normalization and oleanolic acid showed the weakest activity, between 10 and 50 % of normalization. Maslinic acid and oleanolic acid which were used for anti-sickling bioassay were isolated and characterized from Syzygium cordatum by my supervisor, Professor Shode. Others crude extracts and pure isolated compounds were found to be non-active antisickling agents. These included crude hexane and methanol extracts of Cajanus cajan; crude dichloromethane extract of Callistemon viminalis; crude dichloromethane, methanol and 80% aqueous methanol extracts of Melaleuca bracteata; crude hexane, dichloromethane, ethyl acetate, and methanol extracts of Syzygium guineense (South Africa); ursolic acid from Melaleuca bracteata and flavanone glycoside from Syzygium guineense of DRC. This is the first report of the in vitro anti-sickling activity of betunilic acid, betulinic acid acetate, oleanolic acid, and maslinic acid.
A phytochemical investigation of two South African plants with the screening of extractives for biological activity.
(2006) Gallagher, Andrew Bruce.; Koorbanally, Neil Anthony.; Smith, Michael Trevor.
Two South African medicinal plants, Strophanthus speciosus and Eucomis montana, were investigated phytochemically. From Strophanthus speciosus a cardenolide, neritaloside, was isolated, whilst Eucomis montana yielded three homoisoflavanones, 3,9- dihydroeucomin, 4'-demethyl-3,9-dihydroeucomin, and 4'-demethyl-5-0-methyl-3,9- dihydroeucomin. The structures were elucidated on the basis of spectroscopic data. The homoisoflavanones were screened for anti-inflammatory activity using a chemiluminescent luminol assay, modified for microplate usage. All of the homoisoflavanones exhibited good inhibition of chemiluminescence, with IC50 values for 3,9-dihydroeucomin, 4'-demethyl-3,9-dihydroeucomin, and 4'-demethyl-5-0-methyl-3,9- dihydroeucomin being 14mg/mL, 7mg/mL, and 13mg/mL respectively. The IC50 value of 4'-demethyl-3,9-dihydroeucomin compared favourably with the NSAID control (meloxicam), which had an IC50 of 6mg/mL. Neritaloside was not screened for biological activity as the yield of 14.4mg was insufficient for the muscle-relaxant screen for which it was intended. An assay for antioxidant/free radical scavenging activity was also performed. All the compounds had excellent antioxidant/free radical scavenging activity, with percentage inhibition of the reaction being 92%, 96%, and 94% for 3,9-dihydroeucomin, 4'-demethyl- 3,9-dihydroeucomin, and 4'-demethyl-5-0-methyl-3,9-dihydroeucomin respectively at a concentration of 10mg/mL. However, the control compounds, diclofenac and meloxicam, also exhibited strong activity, with the result that the precise mode of anti-inflammatory activity could not be unequivocally determined. The results from the biological screenings thus provided a rational scientific basis for the indigenous ethnomedicinal use of Eucomis species in the treatment of rheumatism, inflammation and pain.
Phytochemistry and bioactive natural products from Lannea alata, Lannea rivae, Lannea schimperi and Lannea schweinfurthii (anacardiaceae)
(2014) Okoth, Akinyi Dorothy.; Koorbanally, Neil Anthony.
Abstract available in PDF file.
The phytochemistry and biological activity of secondary metabolites from Kenyan Vernonia and Vepris species.
(2012) Kiplimo, Joyce Jepkorir.; Koorbanally, Neil Anthony.
This work is an account of the phytochemical analysis of two genera, Vernonia and Vepris which are used as remedies for illness by the Kalenjin community of Kenya. Species of Vernonia are known to yield sesquiterpene lactones, which typify the genus whereas Vepris is rich in alkaloids and limonoids which have a wide range of biological activities. The species studied in this work were Vernonia auriculifera, Vernonia urticifolia, Vepris glomerata and Vepris uguenensis. Phytochemical studies revealed a range of compounds being present in the four species. From Vernonia, triterpenoids, a sesquiterpene amine, a carotenoid and a polyene were isolated. This was the first account of a sesquiterpene amine from a plant species and the first account of the novel polyene. The triterpenoids showed moderate antibacterial activity, with b-amyrin acetate and oleanolic acid being effective at decreasing adhesion of selected gram-negative and gram-positive bacteria. Lutein and urticifolene showed good antibacterial activity against Enterococcus feacium and Pseudomonas aeruginosa. In Vepris, a range of compounds were isolated, belonging to the furoquinoline alkaloids, coumarins, flavonoids, cinnamic acid derivatives, lignins, cinnamaldehydes, triterpenoids and limonoids. Five new compounds; a cinnamaldehyde derivative (glomeral), two flavonoids (veprisinol, uguenenprenol) and two A, D-seco-limonoids (uguenensene and uguenensone) were amongst the compounds isolated. Antibacterial studies showed that glomeral inhibited the growth of Staphylococcus aureus and Shigella dysentrieae at low concentrations (MIC of 2 μg mLˉ¹ and 0.4 μg mLˉ¹ respectively). Antioxidant assays of several compounds revealed that, veprisinol, isohaplopine-3,3’-dimethylallyl ether, uguenenprenol and 7-O-methylaromadenrin are good antioxidant agents. The limonoids isolated from Vepris uguenensis also make up an interesting biogenetic relationship. Structural elucidation was carried out by 1D and 2D NMR spectroscopy in conjuction with mass spectrometry, infrared, ultraviolet and circular dichroism analysis where applicable. Biological assays were carried out using standard methods at laboratories in the University of KwaZulu-Natal and Kenya Medical Research Institute (KEMRI-Nairobi).
Phytochemistry and quorum sensing inhibitory studies of four vernonia species growing in Nigeria.
(2017) Abubakar, Babando Aliyu.; Koorbanally, Neil Anthony.; Moodley, Brenda.
Abstract available in PDF file.
Synthesis and biological activities of 2-hydroxyphenylacyl azoles and their oxime derivatives.
(2012) Cheddie, Adele.; Koorbanally, Neil Anthony.
Fourteen phenylacyl and 2-hydroxyphenylacyl azoles and their oxime derivatives of which three were new, 2-(2-methyl-1H-imidazol-1-yl)-1-phenylethanone oxime 7; 1-(2- hydroxyphenyl)-2-(2-methyl-1H-imidazol-1-yl)ethanone oxime 13 and 1-(2-hydroxyphenyl)- 2-(1H-1,2,4 traizol-1-yl)ethanone oxime 14. The yields obtained for the ketone derivatives were between 50 and 60%, and between 80 and 95% for the oxime derivatives. All compounds were characterized using NMR, IR, UV and GCMS, and were tested for their antifungal and antibacterial activity. These compounds possessed moderate antifungal and weak antibacterial activity, with compound 12, 1-(2-hydroxyphenyl)-2-(1H-imidazol-1- yl)ethanone oxime showing the highest antifungal activity with a MIC value of 1 μg mL̹̹̹⁻¹. In general, the 2'-hydroxy substituted compounds were shown to have better antifungal and antibacterial activity than the unsubstituted compounds.
Synthesis and biological activity of quinoline derivatives.
(2018) Govender, Hogantharanni.; Koorbanally, Neil Anthony.
A total of 42 compounds, which include 12 quinoline-3-carboxamides (A5a-l), 15 quinolone thiosemicarbazones (B5a-o) and 15 tetrazoloquinoline phenylhydrazones (C5a-o) were successfully synthesized and characterised. Of these 42 compounds, 36 have been prepared for the first time in this work, with 4 thiosemicarbazones and 2 phenylhydrazones being previously reported. The 2-chloroquinoline-3-carbaldehyde intermediate was the basic scaffold on which the three types of quinoline hybrids were based on. Various substituents were placed at C-6 on this substituent to create small libraries of compounds. This key intermediate was prepared using the Vilsmeier-Haack reaction, which resulted in a quinoline with a carbaldehyde at C-3. In the case of the quinoline-3-carboxamides, the aldehyde at position 3 was oxidized to the acid functionality via the Pinnick Oxidation. This was followed by the preparation of carboxamides using a coupling reaction with different substituted anilines and using the coupling reagents EDC∙HCl and HOBt in the presence of triethylamine used as a base. The thiosemicarbazones were prepared by condensing the 2-quinolone carbaldehydes with thiosemicarbazides and the tetrazolophenylhydrazones prepared by first forming a tetrazolo ring with sodium azide on the quinoline and then forming phenylhydrazones from the carbaldehyde moiety and phenylhydrazines. The quinoline scaffold was varied at C-6 with Cl, F, Br and CH3 groups and the various hybrids were varied again using different anilines, thiosemicarbazides and phenylhydrazines. The structures of the synthesised compounds were elucidated using 1D and 2D NMR spectroscopy. The synthesised compounds were tested for their antibacterial activity against two Gram positive (Staphylococcus aureus and S. aureus Rosenbach (MRSA)) and four Gram negative species, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Salmonella typhimurium. Although compounds in all three classes of hybrids showed antibacterial activity, these were not as good as current drugs being used as antibiotics. The synthesised compounds showed antibacterial activity in the range of 0.80 to 36.49 mM.
Synthesis and biological evaluation of fluorinated derivatives of 2-styrylchromones and 2-thioxo imidazole dicarboxylate esters.
(2012) Momin, Mehbub I. Khalil.; Koorbanally, Neil Anthony.; Ramjugernath, Deresh.
Two classes of fluorinated derivatives were synthesized in this work to test the effects of the fluorinated drugs in antibacterial, antioxidant and anti-platelet activity. These two classes were the 2-styrylchromones and the 2-thioimidazoles. The 2-styrylchromones were tested for their antibacterial activity and the 3-hydroxypentadien-1one intermediates were tested for their antioxidant activity. The 2-thioimidazoles were tested for the ability to inhibit platelet aggregation in vitro. A total of ten 2-styrylchromones together with their intermediates were synthesized of which six were new(A5a-A5f). The two intermediates to each of the six compounds were also new and together with the 2-styrylchromones resulted in thirty compounds being synthesised and characterised. The synthesis was based on the Baker-Venkataraman rearrangement using substituted cinnamic acids and hydroxyacetophenones.All the 2-styrylchromones were screened for their antibacterial activity using Gram-positive bacteria (Staphylococcus aureus,scuii and xylosus and Bacillussubtilis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosaand Klebsiella pneumonia). The compounds were most effective against B. subtilis followed by S. aureus and a single strain of E. coli (ATCC 25922). Difluorination on the phenyl ring was shown to enhance antibacterial activity and fluorine substitution at the 6-position was shown to be far superior to substitution at the 7-position. In comparison to tetracycline, the activity indices of the fluorinated styrylchromones ranged from 0.50 to 0.75 against B. subtilis. The fluoro and methoxy analogues of (2Z, 4E)-3-hydroxy-1-(2-hydroxyphenyl)-5-(phenyl) penta-2, 4-dien-1-one, the intermediates to the 2-styrylchromones were tested for their ability to act as antioxidants since they contained a 3-hydroxy group in the backbone of their structure. They were screened by the 2, 2-diphenyl-1-pycryl-hydrazyl (DPPH) radical scavenging assay and Ferric Reducing Power assay (FRAP).All the methoxylated analogues showedbetter activity thanthe fluorinated analogues and comparable to that of ascorbic acid. Seven fluorinated derivatives of diethyl-2-(benzylthio)-2,3-dihydro-1H-imidazole-4,5- dicarboxylate (B6a-B6g) as well as a nitro and chloro derivative (B6h-B6i) also known as 2- thiomidazole derivativeswere prepared in five steps from glycine, ethyl formate, diethyl oxalate, potassium thiocyanate and substituted benzyl bromides. The synthesized compounds exhibited concentration dependent anti-platelet aggregation activity on both the thrombin and ADP induced platelet aggregation. The 4-nitro and 4-fluoro compounds exhibited the highest activity from the compounds tested, with estimatedIC₅₀ values of 1.05 and 0.99 mM for the thrombin-induced and ADP-induced platelet aggregation respectively. Three of the compounds, the 3,4-difluoro(B6c), 4-nitro(B6h) and 3-chloro(B6i) derivatives have reasonable activity in both of the assays and could have potential as broad spectrum antiplatelet inhibitors. With the exception of B6c, the fluoro derivatives were not as active as the nitro and chloro compounds. All the reactions in this work were monitored by ¹H and ¹³C NMR at each step and all compounds were characterized using 1D and 2D NMR as well as MS, IR and UV data. All the synthesised compounds were fully characterised unambiguously and the respective carbon and proton resonances were assigned with the aid of HSQC, HMBC and NOESY data. In addition, crystal structures of two 2-styrylchromones and three of its cinnamate ester intermediates as well as the 2-thioimidazole provide a full structural analysis of the compounds synthesised.
Synthesis and biological studies of novel pyranochromene derivatives.
(2015) Pawar, Sunayna Sachin.; Koorbanally, Neil Anthony.
Abstract available in PDF file.