Chemical compositions and Antimicrobial activity of Amaranthus hybridus, Amaranthus caudatus, Amaranthus spinosus and Corriandrum sativum.

Abstract

Different communities in Kenya use a wide variety of indigenous plants for food. About 850 species of plants are used for food. To this group belong Amaranthus species that has important nutrients and a rich array of biologically active secondary metabolites. Corriandrum sativum is a leafy spice/ herb that contain volatile oils from which it derives its flavour and aroma and also antimicrobial properties. Essential oils from fresh leaves of C. sativum were extracted by hydro distillation using a modified Clevenger–type system, analysed by gas chromatography–mass spectroscopy (GC–MS) and evaluated for antimicrobial activity. Subsequently, minimum inhibitory concentration was determined by serial dilution of the oil. Powdered samples of A. hybridus, A. caudatus and A. spinosus were sequentially extracted using hexane, ethyl acetate, dichloromethane and methanol. The resultant extracts were subjected to chemical and antimicrobial activity. Part of the samples underwent protein extractions which were tested for antimicrobial activity. The oil was obtained in 0.04% w/w yield with twenty seven components. The oil was dominated by aldehydes (56.07%), and alcohols (41.33%). The major constituents were 2E-decenal (15.88%). decanal (14.29%), 2E-decen-1-ol (14.22%) and n-decanol (13.64%) Oxygenated monoterpene present was linalool which was 0.32% of the oil. The oil showed activity against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabilis, Salmonella typhi, Bacillus spp and Candida albicans though inactive against Pseudomonas aeruginosa. All the Amaranthus species showed the presence of flavonoids, steroids, terpenoids and cardiac glycosides which are known to have antimicrobial activity. The extracts showed antimicrobial activity against E. coli, S. aureus, K. pneumoniae, P. mirabilis, P. aeruginosa, S. typhi, Bacillus spp and C. albicans. Serial dilution of the active extracts was done to concentrations of 20%, 25%, 33% and 50% for MIC analysis. The MIC’s of the active fractions from Amaranthus species against the tested organisms varied between 129 mg/ml and 755 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.