Biological and Phytochemical Studies of Medicinal Plants, Antidesma venosum (Euphorbiaceae) and Kotschya africana (Fabaceae) used in Traditional Medicine in Kenya

Abstract

Kotschya africana and Antidesma venosum plants are widely used in traditional medicine to treat bacterial, fungal and viral infections. As a result there is need to investigate extracts of these plants and to provide scientific proof for their wide application in traditional medicine system. Extraction of leaves, stem and roots of K. africana and A. venosum using solvents of increasing polarity, namely, hexane, dichloromethane, ethyl acetate and methanol respectively afforded dry extracts. The extracts were tested for anti-fungal and anti-bacterial activities, for brine shrimp toxicity test and anti-oxidant activities. Using the disc diffusion method, it was demonstrated that extracts of the leaves, stem and roots of these plants have moderate anti-bacterial activities against Escherichia coli and Staphylococeus aureus and low anti-fungal activity against Candida albicans. The root extracts were the most active followed by the stem and the leaf extracts. Extracts from these plants also exhibited mild cytotocixity to brine shrimp larvae with LD50 values ranging from 89.21 to 3876.69 for K. africana and 32.61 to 2515.39 for A. venosum. The results support the traditional uses of extracts of these plants for the management of bacterial and fungal infections. Five compounds were also isolated and identified. From the roots of A. venosum, 3,5,7,3´,4´-pentahydroxyflavanol commonly known as epicatechin, 5,7,8,2´,3´,4- hexahydrodihydroflavanol-4-O-β-D-glucoside, and 5,7,4´-trihydroxyl-isoflavone (genistein) were isolated. Lupeol and compound 25 were isolated from K. africana leaves. Compound 25 was a diterpenoid with the labdan skeleton. xxii Anti-oxidant screening of semi-pure compounds and fractions and a pure compound from K. africana and A. venosum, showed that the semi-pure compounds, KAL11 and KAL227302 had the lowest radical scavenging characteristics at a loading of 50 μg. β-sistosterol, lupeol and AVLHB36 had moderate scavenging characteristics while the fraction AVRM8286 had the highest radical scavenging activity at a loading of 0.5 μg. Ascorbic acid (standard) showed activity at the lowest loading of 0.05 μg.