Phytochemical constituents and antimicrobial activity of leaf extracts of three <i>Amaranthus</i> plant species

Abstract

This study investigated the phytochemical constituents and antimicrobial activity of hexane, ethyl acetate, dichloromethane and methanol leave extracts of Amaranthus hybridus, Amaranthus spinosus and Amaranthus caudatus. The microorganisms assayed for antimicrobial activity were: the grampositive Staphylococcus aureus and Bacillus spp, the gram-negative Escherichia coli, Salmonella typhi, Pseudomonas aeruginosae, Proteus mirabillis and Klebsiella pneumoniae and a pathogenic fungus Candida albicans. The leave extracts showed a broad spectrum anti-bacterial activity but resistance to the fungus. Commonly encountered phytochemical constituents in the leaf extracts of the three Amaranthus species included flavonoids, steroids, terpenoids and cardiac glycosides. The minimum inhibitory concentration (MIC) exhibited by A. spinosus extracts against the Salm. typhi was 129 mg/ml. The MIC exhibited by A. hybridus extracts against the tested organisms ranged between 200 and 755 mg/ml whereas that of A. caudatus was between 162.2 and 665 mg/ml. The antimicrobial properties of these plants which have been used by mankind for centuries without any signs of toxicity can be used in the traditional herbal medicines which play a very important role in primary care systems in the developing world and are becoming increasingly popular in the developed world.