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ABSTRACTThis study determines the phytochemical contents of selected medicinal plant extracts quantitatively using spectrophotometry and to evaluate their safety on mammalian cells in vitrousing tetrazolium-based colorimetric cytotoxicity assay. Twenty-two ethanolic plant extracts were assessed, and the result showed that Psidium guajavahad the highest concentration of alkaloids (219.06±11.50mg/g dry-weight (dw)). In contrast, Acacia niloticaleaf extract with 191.60±9.07mg/gdw had the highest level of flavonoids. Vernonia amygdalinaand Moringa oleiferacontained more steroids than the other plant extracts while condensed tannin was highest in Carya illinoinensis(21.72 ± 0.84 mg/g dw). Coffea arabica, Acacia niloticaleaf, Vernonia amygdalina, Carya illinoinensisand Psidium guajavahad more saponins than the other plant extracts. Regarding cytotoxicity evaluation, Allium cepaand Tulbaghia violaceawith concentration killing 50% of cells (LC50) values of 0.5182±0.40 and 0.4909 ± 0.034 mg/ml, respectively, were the safest of all the plant extracts. Acacia niloticapod and Camelia japonicaleaf extracts were the most cytotoxic with LC50values of 0.0101 ± 0.016 and 0.0151 ± 0.005 mg/ml, respectively, which are well below the recommended toxic cut-off point (0.03mg/ml). The best selectivity index (SI) value of 1.061 was obtained with Aloe feroxagainst S. aureus,which is a Gram-positive bacterium.

This study reports the first total synthesis of the bioactive oxepinochromones 12-O-acetyleranthin (8) (angular isomer) and 12-O-acetylptaeroxylinol (9) (linear isomer). The antifungal activity of these compounds and their derivatives was determined against Candida albicansand Cryptococcus neoformans. Most compounds had good selectivity between the two fungi and showed moderate to good activity. 12-O-Acetyleranthin (8) had the highest activity against C. albicans, with an MIC value of 9.9 μM, while 12-O-acetylptaeroxylinol (9), the compound present in Ptaeroxylon obliquum, had the highest activity against C. neoformans, with an MIC value of 4.9 μM.

This study aimed to evaluate the selective cytotoxicity of six natural compounds on four cancerous cells (MCF-7, HeLa, Caco-2 and A549) and two normal intestinal and lung cells (Hs1.Int and Wl-38) cells. We also attempted to analyze basically the structure–activity relationships and to understand the mechanism of action of active compounds using the Caspase-Glo®3/7 kit. Globimetulin B (2) isolated from Globimetula dinklageiwas significantly cytotoxic on cancerous cells with 50% inhibitory concentrations (IC50) ranging from 12.75 to 37.65 μM and the selectivity index (SI) values varying between 1.13 and 3.48 against both normal cells. The compound 3-O-β-d-glucopyranosyl-28-hydroxy-α-amyrin (5) isolated from Phragmanthera capitataexhibited the highest cytotoxic activity on HeLa cells with the IC50of 6.88 μM and the SI of 5.20 and 8.71 against Hs1.Int and Wl-38 cells, respectively. A hydroxyl group at C-3 of compounds was suggested as playing an important role in the cytotoxic activity. The induction of caspase-3 and -7 activity represents some proof that apoptosis has occurred in treated cells. Globimetulin B (2) selectively killed cancer cells with less toxicity to non-cancerous cells as compared to conventional doxorubicin therapy.

Twenty‐six plants used by Zulu healers for the treatment of pain and inflammation were assayed for cyclooxygenase inhibitory activity. The plant parts used by the traditional healers were dried and milled. Ethanol and aqueous extracts of the plants were prepared and assayed. Several plant extracts exhibited high inhibitory activity in the assay. Among these were Acacia rehmanniana, Cryptocarya latifolia, Dichrostachys cinerea, Erythrophleum lasianthum, Euclea natalensis, Felicia muricata, Mohria caffrorum, Phygelius capensis, Siphonochilus aethiopicus, Trichilia emeticaand Turraea floribunda. The ethanol extracts generally showed higher activity than the aqueous extracts. © 1997 by John Wiley & Sons, Ltd.

Twenty-six plants used by Zulu healers for the treatment of pain and inflammation were assayed for cyclooxygenase inhibitory activity. The plant parts used by the traditional healers were dried and milled. Ethanol and aqueous extracts of the plants were prepared and assayed. Several plant extracts exhibited high inhibitory activity in the assay. Among these were Acacia rehmanniana, Cryptocarya latifolia, Dichrostachys cinerea, Erythrophleum lasianthum, Euclea natalensis, Felicia muricata, Mohria caffrorum, Phygelius capensis, Siphonochilus aethiopicus, Trichilia emetica and Turraea floribunda. The ethanol extracts generally showed higher activity than the aqueous extracts. © 1997 by John Wiley & Sons, Ltd.