Bioassay-guided Isolation of Antidermatophytic Compounds from Piper longum L.

Aims: Piper longum, a medicinal plant, grows wildly in Northeast India. In our earlier study, the chloroform extract from leaves of P. longum L. (Piperaceae) exhibited promising in vitro antidermatophytic activity. The present investigation was undertaken to isolate and identify the antidermatophytic compounds present in P. longum (leaf).

Study Design: Air dried powdered leaves (100 g) of P. longum were extracted with petroleum ether. After removal of the petroleum ether soluble part, the residue left over was extracted with chloroform. The solvent was evaporated under reduced pressure at 40°C using rotary evaporator, lyophilized and kept in glass vials till further use. Chloroform extract was subjected to bioassay-guided fractionation using column chromatography. Antidermatophytic activity of the isolated fractions was determined by broth microdilution assay. Chemical compounds were identified by GC-MS analysis.

Place and Duration of Study: Defence Research Laboratory, Tezpur, Assam, India and Department of Botany, Gauhati University, Guwahati, Assam, between Jan 2011 and Oct 2011.

Results: Repeated column chromatography afforded a yellowish semi solid mass. The fraction showed significant antidermatophytic activity with minimum inhibitory concentration (MIC) values of 1.25 mg mL-1 for T. mentagrophytes (MTCC 8476) and 2.5 mg mL-1 for T. rubrum (MTCC 8477). GC-MS analysis of the fraction revealed the presence of nine compounds namely Benzene (2-methyl-1-propenyl) (5.19%), 2,4-Bis (1,1-dimethylethyl)-phenol (8.11%), lb-Bisabolene (12.48%), 2,8-decadiyne (13.79%), Methyl 14-methylpentadecanoate (15.41%), methyl linolenate (25.52%), octadecanoic acid, methyl ester (5.31%), 11-dodecen-1-ol (7.63%) and dicyclohexyl phthalate (6.54%).

Conclusion: The results highlighted the antidermatophytic potential of P. longum. Further investigation should be focused on the active constituents that could be used for development of antidermatophytic agent.