Bioactive natural products derived from the East African flora.

This review describes bioactive natural products isolated from East African medicinal plants. It includes 211 bioactive compounds from 41 plant species, and cites 116 references.

A novel antiplasmodial 3',5'-diformylchalcone and other constituents of Friesodielsia obovata.

Phytochemical investigation of the stem and root barks of Friesodielsia obovata Benth (Annonaceae) afforded new 3',5'-diformyl-2',4',6'-trihydroxychalcone and N-formyl-7-hydroxyglaucine together with five known compounds, 3',5'-dimethyl-2',4',6'-trihydroxychalcone, (-)-crotepoxide, demethoxymatteucinol, lawinal, and benzyl benzoate. 3',5'-diformyl-2',4',6'-trihydroxychalcone indicated significant antiplasmodial, cytotoxicity, and larvicidal activities.

Methanolic extracts of Aloe secundiflora Engl. inhibits in vitro growth of tuberculosis and diarrhea-causing bacteria.

BACKGROUND: The emergence of resistance to antimicrobials by pathogens has reached crisis levels, calling for identification of alternative means to combat diseases. OBJECTIVE: To determine antimicrobial activity of crude methanolic extract of Aloe secundiflora Engl. from Lake Victoria region of Kenya. MATERIALS AND METHODS: Extract was tested against four strains of mycobacteria (Mycobacterium tuberculosis, M. kansasii, M. fortuitum and M. smegmatis), Salmonella typhi, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae and a fungus Candida albicans. activity of the extract was determined using BACTEC(™) MGIT(™) 960 system. General antibacterial and antifungal activity was determined using standard procedures: zones of inhibition, Minimum Inhibitory Concentrations (MICs) and Minimum Bactericidal/Fungicidal Concentrations (MBCs/MFCs). RESULTS: The extract was potent against M. fortuitum, M. smegmatis and M. kansasii where it completely inhibited growth (Zero growth units (GUs)) in all the extract concentrations used. It gave strong antimycobacterial activity (157 GUs) against M. tuberculosis. It showed strong antimicrobial activity (P≤0.05), giving inhibition zones ≥9.00 mm against most microorganisms, such as P. aeruginosa (MIC 9.375 mg mL(-1) and MBC of 18.75 mg mL(-1)), E. coli (both MIC and MBC of 18.75 mg mL(-1)), S. aureus and S. typhi (both with MIC and MBC of 37.5 mg mL(-1)). Preliminary phytochemistry revealed presence of terpenoids, flavonoids and tannins. CONCLUSION: The data suggests that Aloe secundiflora could be a rich source of antimicrobial agents. The result gives scientific backing to its use by the local people of Lake Victoria region of Kenya, in the management of conditions associated with the tested microorganisms.

A bioactive isoprenylated xanthone and other constituents of Garcinia edulis.

Phytochemical investigation on the root bark of Garcinia edulis (Clusiaceae) gave a new isoprenylated xanthone, 1,4,6-trihydroxy-3-methoxy-2-(3-methyl-2-butenyl)-5-(1,1-dimethyl-prop-2-enyl)xanthone (1), a known xanthone, forbexanthone (2) together with three known pentacyclic triterpenoids, friedelin, lupeol and lupeol acetate. The structure of the new compound was fully characterised by NMR spectroscopic analysis. Compound 1 showed significant anti-HIV-1 protease activity with IC(50) value of 11.3 microg/mL. Furthermore, compound 1 showed potent cytotoxic activity with LC(50) value of 2.36 microg/mL against brine shrimp larva in vitro.

Bioactive isoflavones from Dalbergia vacciniifolia (Fabaceae).

Three new 5-dehydroxy isoflavone compounds, 6,2'-dimethoxy-7,4'-dihydroxyisoflavone (1), 6,2',4'-trimethoxy-7-hydroxyisoflavone (2), and 6,2',4',5'-tetramethoxy-7-O-[beta-D-apiofuranosyl-(1 --> 6)-beta-D-glucopyranoside] isoflavone (3), along with a known isoflavone, 6,2',4',5'-tetramethoxy-7-hydroxyisoflavone (4), were isolated from the ethanolic extract of Dalbergia vacciniifolia Vatke. Their structures were established by spectroscopic techniques including one- and two-dimension NMR. Compound 1 showed mild cytotoxic activity against brine shrimp larvae with a LC50 value of 266 microg/mL.

New furanoditerpenoids from Croton jatrophoides.

Four furanoditerpenoids were isolated from roots of Croton jatrophoides (Euphorbiaceae) collected in Tanzania. In addition to the known compounds penduliflaworosin and teucvin (mallotucin A), a new teucvin isomer, which was named isoteucvin, and a furanoditerpenoid with a new skeleton, for which the name jatrophoidin was adopted, were isolated. Their structures were elucidated by spectroscopic methods such as ESI-MS and NMR, including (1)H-, (13)C-, and two-dimensional NMR. The crystal structures of isoteucvin and jatrophoidin were solved using single-crystal X-ray diffraction, by which we also established the absolute configuration of jatrophoidin. The refined crystal structure of isoteucvin has the same (absolute) configuration as jatrophoidin, although the X-ray diffraction data of isoteucvin were not conclusive with respect to the absolute configuration.

A novel isoflavonoid from Millettia puguensis.

From the roots of Millettia puguensis (Leguminosae), a novel isoflavonoid (5), 2'-methoxy-4',5'-methylenedioxy-7,8-[2-(1-methylethenyl)furo]isoflavone, and four known compounds, i. e., lupeol (1), (-)-maackiain (2), 6,7-dimethoxy-3',4'-methylenedioxyisoflavone (3) and 7,2'-dimethoxy-4',5'-methylenedioxyisoflavone (4) were isolated and identified by 1H-, 13C-NMR and mass spectroscopy. All compounds were evaluated for their antiprotozoal and cytotoxic activities, but only a moderate antileishmanial activity was observed for compound 3 (IC50 = 32 microM against Leishmania infantum), and a moderate cytotoxicity for compound 2 (IC50 = 43 microM on MRC-5 cells).