ANTIMICROBIAL ACTIVITY OF TUBER EXTRACTS OF THE MEDICINAL PLANT Coleus forskohlii

Aims: Coleus forskohlii Briq. (syn. Coleus barbatus Benth.) belongs to the family Lamiaceae is a well known traditional medicinal plant throughout the country and known as ‘pashanbhedi’ in Sanskrit and ‘pathatchur’ in Hindi is one of the most potential medicinal plants of the future, as it’s pharmacoproperties have been discovered only recently. Its tuberous roots are found to be rich source of forskolin which is being used as a remedy for hypertension, glaucoma, asthma, congestive heart failures and certain types of cancers and also individual use as vegetables. Keeping the above views in mind, the present investigation was undertaken to study the antimicrobial activity of tuber extracts of C. forskohlii. The MIC level of different tuber extracts (11, 33 and 55 µg ml-1) was also studied.

Study Design: In the present study, Well diffusion assay was done for both gram positive and gram negative strains such as Staphylococcus aureus, Escherichia coli, Pseudomonas sp. and Vibrio cholerae. Three fungi were used in the study were Alternaria alternata, Curvularia lunata and Fusarium oxysporum which were maintained on potato dextrose agar slant at 4°C in our Laboratory. Different concentrations (11 µg, 33 µg and 55 µg ml-1) of the crude chloroform extract of C. forskohlii were subjected to antifungal activity assay by poisoned food technique.

Place and Duration of Study: Sample: Coleus plants were grown in the experimental field of the Department of Botany, Burdwan University. The tubers of Coleus were collected during the months of December, 2011 to February, 2012.

Results: The higher inhibition zone was recorded in Pseudomonas sp. which was 3.5 cm. S. aureus showed lowest inhibition zone of 2.0 cm. It is interesting to note that higher mycelial growth inhibition was found in C. lunata (76.70% at 11 µg ml-1 tuber extract) followed by A. alternata (68.20% at 11 µg ml-1 tuber extract) and F. oxysporum (65.84% at 11 µg ml-1 tuber extract). The 100% mycelial growth inhibition of the three phytopathogenic fungi was observed at the conc. level of 33 µg ml-1 of Coleus tuber extract and 55 µg ml-1 of Coleus tuber extract. Out of the three fungi, C. lunata was found to be more vulnerable to growth inhibition by tuber extract.

Conclusion: These results indicate that the extracts of Coleus tuber have a potential broad spectrum antimicrobial activity.