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The stem bark of Cassia sieberiana was extracted with methanol and the methanol extract partitioned with chloroform. Column chromatography of the chloroform fraction over silica gel yielded a novel benzofurochromene [2-(4-hydroxylphenyl)-7’-1, 2-dihydroxy-1-phenylpropyl)-4’, 6’-dihydroxy [1] phenylbenzofuro (2, 3-c)-7’-chromene], lupeol and epiafzelechin. Their structures determined by Nuclear Magnetic resonance and mass spectrometry.

Ethnopharmacological relevance: \ud \ud Leaves from the plant species studied herein are traditionally used in northern Nigeria against various protozoan infections. However, none of these herbal preparations have been standardized, nor have their toxicity to mammalian cells been investigated. In search of improved and non-toxic active antiprotozoal principles that are not cross-resistant with current anti-parasitics, we here report the results of the in vitro screening of extracts from seven selected medicinal plant species (Centrosema pubescens, Moringa oleifera, Tridax procumbens, Polyalthia longifolia, Newbouldia laevis, Eucalyptus maculate, Jathropha tanjorensis), used traditionally to treat kinetoplastid infections in Nigeria, and the isolation of their bioactive principles.\ud \ud Aim of the study: \ud \ud To investigate the efficacies of medicinal plant extracts, and of compounds isolated therefrom, against kinetoplastid parasites, assess cross-resistance to existing chemotherapy, and assay their toxicity against mammalian cells in vitro.\ud \ud Material and methods: \ud \ud Plants were extracted with hexane, ethyl acetate and methanol. Active principles were isolated by bioassay-led fractionation, testing for trypanocidal activity, and identified using NMR and mass spectrometry. EC50 values for their activity against wild-type and multi-drug resistant Trypanosoma brucei were obtained using the viability indicator dye resazurin.\ud \ud Results: \ud \ud Seven medicinal plants were evaluated for activity against selected kinetoplastid parasites. The result shows that crude extracts and isolated active compounds from Polyalthia longifolia and Eucalyptus maculata, in particular, display promising activity against drug-sensitive and multi-drug resistant Trypanosoma brucei. The EC50 value of a clerodane (16α-hydroxy-cleroda-3,13(14)-Z-dien-15,16-olide) isolated from Polyalthia longifolia was as low as 0.38 µg/mL, while a triterpenoid (3β,13β-dihydroxy-urs-11-en-28-oic acid) isolated from Eucalyptus maculata displayed an EC50 of 1.58 µg/mL. None of the isolated compounds displayed toxicity towards Human Embryonic Kidney cells at concentrations up to 400 µg/mL. In addition, the isolated compounds were active against Leishmania mexicana, as well as against T. congolense.\ud \ud Conclusion: \ud \ud We have isolated a clerodane compound from Polyalthia longifolia that shows low toxicity, no cross-resistance with current treatments, and promising activity against both human-infective and veterinary Trypanosoma species.

Chemical investigation of ethyl acetate leaf-extract of Pterocarpus santalinoides led to isolation of a friedelane-terpenoid. Structure elucidation was done by comparison of the Nuclear Magnetic Resonance (NMR) spectral features with literature data and was consistent with reported values for friedelan-3-one. The following microorganisms (Clinical isolates): methicillin resistant Staphylococcus aureus (MRSA), S. aureus, Corynebacterium ulcerans, Streptococcus pneumoniae, Campylobacter jejuni, Helicobacter pylori, Escherichia coli, Shigella dysenteriae, Candida tropicalis and Candida krusei were used for the in vitro antimicrobial activity. The isolated compound had Minimum Inhibition Concentration (MIC) value of 10 μg/ml for MRSA, H. pylori, E. coli and Minimum Bactericidal/Fungicidal Concentration (MBC/MFC) of 40 μg/ml for E. coli; 20 μg/ml for MRSA, H. pylori and C. krusei; 10 μg/ml for S. aureus, S. pneumonia and C. tropicalis. It showed moderate antimicrobial activity against most of the pathogens tested. This is also the first report of the isolation of friedelan-3-one from this species.Key words: Friedelan-3-one, methicillin resistant Staphylococcus aureus (MRSA), Helicobacter pylori, Escherichia coli.