Anti-microbial activity, toxicity and chemical characterization of extracts of Indigofera Lupatana Baker F. plant

Abstract

Indigofera lupatana Baker F. (locally known as Mugiti) has been used by Mbeere community of Kenya to treat cough, diarrhea, pleurisy and gonorrhea. These and other infectious diseases are a cause of morbidity and mortality in humans and animals. Their effects are further aggravated by drug resistance. There is also increased emergence and re-emergence of infections from previously harmless micro-organisms, as part of nosocomial and opportunistic infections. This calls for search of new drugs that will mitigate these problems. Indigenous plants are promising as a cheap alternative source of new therapeutic agents. Although the use of phytomedicine has been in practice for long, little has been done to evaluate their effectiveness, safety, target organisms and also their chemical characterization. Therefore, the aim of this study was to investigate the antimicrobial activity, toxicity and phytochemical screening of root extracts of Indigofera lupatana Baker F. Powdered sample of I. lupatana Baker F. roots were sequentially extracted using hexane, ethyl acetate, dichloromethane and methanol solvents. The resultant fractions were subjected to anti-bacterial assay, phytochemical tests and brine shrimp toxicity bioassay. The fractions showed the highest activity against Bacillus subtilis (28.5 ± 0.3mm), Staphylococcus aureus (22.6 ± 1.0mm), Bacillus cereus (22.0 ± 0.3mm), Escherichia coli (21.7 ± 0.7mm), Pseudomonas aeruginosa (21.5 ± 0.9mm), Salmonella typhimurium (17.3 ± 0.3mm), Klebsiella pneumonia (15.3 ± 0.4mm) and Proteus mirabilis (12.3 ± 0.5mm). The activity was greater among the Gram positive bacteria than Gram negative bacteria. Activity of the ethyl acetate, dichloromethane and methanol extracts on bacillus cereus species and that of ethyl acetate on P. aeruginosa was similar to the activity of chloramphenicol drug (with P > 0.05). The MIC ranged from between 21.9 to over 750mg/ml. Phytochemical testing revealed presence of Phenolics, Flavonoids, Tannins, Saponins, Terpenoids, Cardiac glycosides, Steroids and Phlobatannins which are responsible for the bioactivity of the sample fractions. All fractions had LC50 value greater than 1000μg/ml which is an indication that they are all non toxic. Therefore Indigofera lupatana Baker F. can be used as an alternative source of new, effective, safe drug(s) against the tested microbes because it demonstrated antibacterial efficacy with no toxicity to brine shrimps.