Bioassays guided fractionation of Coronopus didymus for its antifungal activity against Sclerotium rolfsii.

Sclerotium rolfsii Sacc. is a pathogen of about 500 plant species. In a laboratory screening bioassay, methanolic extracts of 15 mg mL⁻¹ concentrations of different parts of Coronopus didymus (L.) Sm. (Brassicaceae) namely leaf, stem, inflorescence and root reduced the biomass of S. rolfsii by 67%, 26%, 40% and 58%, respectively. Methanolic root extract was successively fractionated with n-hexane, chloroform, ethyl acetate and n-butanol. All the concentrations (3.125-200 mg mL⁻¹) of ethyl acetate fraction completely inhibited the target fungal growth. Two compounds A and B were separated from this fraction by Thin Layer Chromatography (TLC). TLC fraction A was found highly effective against S. rolfsii with MIC value 15.62 µg mL⁻¹ as compared to MIC value 7.81 µg mL⁻¹ of the commercial fungicide mencozeb. This compound may be used for the synthesis of natural product based fungicide for the control of S. rolfsii.