Antimicrobial, phytochemical and cytotoxicity activities of extracts of Lannea welwitschii (Hiern) Engl. (Annacardiaceae)

Abstract

Towards-discovering new agents to treat microbial infections, methanolic extracts of leaves, stem and roots of Lannea welwitschii were screened for antibacterial and antifungal activity against Staphylococcus aureus (ATCC 25923), Bacillus subtilis (ATCC 6633), Pseudomonas aeruginosa (ATCC 27853), Salmonella typhimurium (ATCC 14028), Proteus vulgaris (ATCC 6380), Escherichia coli (ATCC 25922), Rhizopus spp. (Lab Stock) and Candida albicans (ATCC 18804). Agar cup diffusion method was used to determine zone of inhibition while Minimum Inhibitory Concentration (MIC) on Staph, aureus and E. coli were determined by agar dilution method. Phytochemical screening was done to determine the type of secondary metabolite while cytotoxicity was determined by Brine-Shrimps Lethality (BSL) assay. All the plant parts showed antimicrobial activity against all the test organisms with zone of inhibition of 11.0-20.0 mm, and MIC of 0.31 and 0.62mg/ml on Staph, aureus (ATCC 25923) and E. coli (ATCC 25922) respectively. The LC50 from the cytotoxicity test (BSL) were 196.49 and 100.00 µg/mL for the leaves and stem extracts respectively. Saponins, tannins, cardiac glycosides (steroids) and flavonoids were detected. Therefore L. welwitschii as a medicinal plant contains metabolites having broad spectrum antimicrobial activity, and the methanolic extracts were relatively non-toxic..