Evaluation of extracts of <i>Coleus</i> species for antibacterial activity

Abstract

Antibacterial activity of 50%-methanol, water and absolute methanol extracts of Coleus species (whole plant) was evaluated using agar, and macro-broth dilution methods. The test microorganisms were strains of Staphylococcus aureus, Escherichia coli, Salmonella typhi and Pseudomonas aeruginosa. The yields achieved with extracts were 24% for absolute methanol, 22% for the water and 39% for the 50% methanol extracts, respectively. The phytochemical analysis of the extracts revealed the presence of flavonoids, alkaloids, tannins, cardiac glycosides, carbohydrates, steroids, proteins, glycosides and anthracene glycosides. All four (100%) bacterial strains were susceptible to all the extracts with inhibition zone diameter (IZD) ranges of 15-24 mm and minimum inhibition concentrations (MICs) of 1.95-100 mg/ml; and these are consistent with the time kill observed with the extracts. Results authenticate the folklore medicinal usage of Coleus species for treatment of diseases such as gastroenteritis and skin infections.

Key words: Antibacterial activity, Coleus species, Cameroon