Ofentse Mazimba

Tylosema esculentum extractives and their bioactivity

The investigation of Tylosema esculentum (Morama) husks, cotyledons, and tuber yielded griffonilide 2, compound 1, griffonin 3, gallic acid 4, protocatechuic acid 5, β-sitosterol 6, behenic acid 7, oleic acid 8, sucrose 9, 2-O-ethyl-α-D-glucopyranoside 10, kaempferol 11 and kaempferol-3-O-β-D-glucopyranoside 12. The structures of the isolates were determined by NMR, HR-TOF EIMS, IR and UV-vis spectroscopy, and by comparison with literature data. The husk EtOAc and n-butanol extracts demonstrated >90% DPPH radical scavenging activity at concentrations of 25, 50 and 250 μg/mL. Furthermore the husk extracts showed higher total phenolic content (233 mg GAE/g). The extractives exhibited minimum inhibitory quantities of 50-100 μg or no activity against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Candida albicans. The tuber extracts were inactive against Caco-2 and Hela cell lines, while the husk extracts showed low activity against Caco-2 and Vero cell line with IC(50) values >400 μg/mL. The GC-MS analysis showed the beans and tuber non-polar (n-hexane) extracts major constituents as fatty acids.

Antioxidant and antimicrobial studies on fused-ring pyrazolones and isoxazolones.

A series of 3-nitrochalcones have been synthesized enroute towards fused ring pyrazolones and isoxazolones. Base catalyzed condensation of the chalcones with ethylacetoacetate yielded cyclohexenones in good yields (74-76%). The treatment of cyclohexenones with hydrazine hydrate or hydroxylamine chloride in the presence of a base afforded the corresponding fused-ring pyrazolinones (70-78% yield) and isoxazolinones (58-66% yield). The newly synthesized compounds were characterized by IR, 1D and 2D NMR and HRMS spectral analysis. The compounds were screened for their antioxidant and antimicrobial activities. Pyrazolinones showed good DPPH radical scavenging and iron metal chelating properties. The para-hydroxy group was important for a compound to have enhanced antioxidant activity. Pyrazolinones and isoxazolinone exhibited a wider range of antimicrobial activities compared to cyclohexenones. Pyrazolinones and isoxazolinone bearing a thiophene ring were the most potent type of compounds against Bacillus subtilis and Candida albicans with MIC values of 0.313-1.25 μg/mL. Some of the synthesized compounds were found to have promising antioxidant, metal chelation and antimicrobial activities.

Therapeutic and Prophylactic Potential of Morama (Tylosema esculentum): A Review.

Tylosema esculentum (morama) is a highly valued traditional food and source of medicine for the San and other indigenous populations that inhabit the arid to semi‐arid parts of Southern Africa. Morama beans are a rich source of phenolic acids, flavonoids, certain fatty acids, non‐essential amino acids, certain phytosterols, tannins and minerals. The plants tuber contains griffonilide, behenic acid and starch. Concoctions of extracts from morama bean, tuber and other local plants are frequently used to treat diarrhoea and digestive disorders by the San and other indigenous populations. Information on composition and bioactivity of phytochemical components of T. esculentum suggests that the polyphenol‐rich extracts of the bean testae and cotyledons have great potential as sources of chemicals that inhibit infectious microorganisms (viral, bacterial and fungal, including drug‐resistant strains), offer protection against certain non‐communicable diseases and promote wound healing and gut health. The potential antinutritional properties of a few morama components are also highlighted. More research is necessary to reveal the full prophylactic and therapeutic potential of the plant against diseases of the current century. Research on domestication and conservation of the plant offers new hope for sustainable utilisation of the plant. Copyright

Xanthones and Anthranoids from the Medicinal Plants of Africa

Xanthones or xanthen-9H-ones (dibenzo-gamma-pirone) comprise an important class of oxygenated heterocycles whose role is well known in medicinal chemistry. The biological activities of this class of compounds are associated with their tricyclic scaffold but vary depending on the nature and/or position of the different substituents. In this chapter, the biosynthetic pathways of xanthones and anthrones (or anthronoids) are examined, and we summarize the occurrence of these two classes of compounds in African plants, together with their biological/pharmacological activities. It appears that most xanthones identified so far in plants of the continent were isolated from the family Guttiferae. The present literature review revealed 97 compounds (86 xanthones and 11 anthranoids), of which 46 were reported for the first time. The biological activity reported for such compound includes antimicrobial, cytotoxic, and enzyme inhibitory effects.

A flavanone and antimicrobial activities of the constituents of extracts from Mundulea sericea.

In this study, 12 compounds, which include a new flavanone 5-methoxy mundulin (1), were isolated from the leaves, stem bark and twigs of Mundulea sericea (Willd.) A. Chev. (Fabaceae; Papilionoideae). The structures of the compounds were identified based on spectral data analyses. The constituents of M. sericea also showed antimicrobial activities (MIQ = 0.01–100 µg) against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Candida albicans.

Fatty Acid Composition and Antimicrobial Activity of Baphia massaiensis Seed Oil

Aims: The seed oil composition of Baphia massaiensis seeds was determined using H NMR and GC-MS techniques. The seed oil was also screened for antimicrobial activity. Study Design: The study was designed to determine Baphia massaiensis seed oil fatty acid composition and antimicrobial activity. Place and Duration of Study: Department of Chemistry, University of Botswana, between June 2012 and July 2014. Methodology: The Baphia massaiensis seed cotyledons powder (29.2 g) were extracted by Soxhlet extraction using n-hexane/ 1-propanol. The seed oil (3.12 g) was esterified to FAMEs using dry methanol. The percentage composition of fatty acids methyl esters (FAMEs) in the seed oil of B. massaiensis was determined using H NMR and GC-MS techniques. The antimicrobial screening was carried out using agar well diffusion method. Results: The H NMR method showed the oil composition to be 20% ω-3 fatty acids, 11% monounsaturated, 60% di-unsaturated and 9% saturated fatty acids. Based on GC-MC analysis, Short Research Article Keroletswe et al.; JOCAMR, 2(3): 1-7, 2017; Article no.JOCAMR.32553 2 saturated fatty acids composition was 12.2% and unsaturated fatty acids were 87.8% of the total FAMEs. The major constituents of B. massaiensis seed oil FAMEs were linoleic acid (C18:2; 49.0%) and linolenic acid (C18:3; 36.7%) methyl esters. The FAMEs were active against E. coli, S. aureus and B. subtilis with 10-16 mm inhibition zones. Conclusion: Linoleic acid (49.0%) and linolenic (36.7%) methyl esters were the major components of Baphia massaiensis FAMEs.

NaBH4-Mediated Complete Reduction of the α,β-Unsaturated Ketone Units of Chalcones in the Synthesis of Flavans

In this chapter, the NaBH4-mediated reduction of both the carbon-carbon double bond and the carbonyl group of chalcones and subsequent acid mediated cyclisation of the resulting saturated alcohols to flavans is described. The chalcones were readily prepared from commercially available acetophenone and salicylaldehyde derivatives. Through this sequence of reactions, 3′,4′-dimethoxyflavan and 3′,4′,8-trimethoxyflavan were prepared in good overall yields.