Antimicrobial Investigation of Medicinally Important Coleus Species

Plants having antimicrobial properties have been reported as an important natural source of bioactive compounds. One of such plants includes various species of Coleus from the family Lamiaceae. These are known for their medicinal uses in treatment of various ailments like digestive disorders, asthma, hypertension, heart diseases, and various cancers. This work was carried out to study the antimicrobial potential and genetic variability of three species of Coleus plants; C. amboinicus, C. aromaticus, and C. forskohlii. Plant extracts were obtained by using four different organic solvents; butanol, methanol, ethanol, and acetone. The antimicrobial activity was tested against various bacteria including Escherichia coli, Bacillus sp., Staphylococcus sp., Proteus sp., and Pseudomonas sp. by using agar diffusion technique. MIC analysis was also done for effective plant extracts. Out of all four solvents, butanol was found to be the most potent solvent showing maximum inhibition in C. forskohlii, exhibiting maximum inhibition against E. coli and Proteus sp. Moderate activity was noted in methanolic extracts whereas minimum inhibition occurred in ethanol and acetone extracts. It can be concluded from this study that Coleus plants, especially C. forskohlii, exhibit high levels of antimicrobial activity and could therefore serve as valuable sources for natural antimicrobial substances