Title : Bioassays Guided Fractionation of Ageratum conyzoides for Identification of Natural Antifungal Compounds against Macrophomina phaseo
Macrophomina phaseolina is a soil-borne fungal pathogen causing diseases in more than 500 plant species. The present study aimed to identify possible antifungal constituents in different parts of an asteraceous weed Ageratum conyzoides for the control of M. phaseolina through bioassays guided fractionation. Different parts of the weed were extracted in methanol and antifungal bioassays were carried out using different concentrations (1, 2, …5%) of the extract. Stem extract caused the highest inhibition in fungal biomass (20-83%) followed by leaf extract (16-67%). Methanolic stem extract was partitioned using four organic solvents. Bioassays carried out with different concentrations (3.125 to 200 mg mL-1) of the sub-fractions of methanolic stem extract revealed the highest antifungal potential of chloroform sub-fraction with 56-93% reduction in fungal biomass followed by n-butanol, ethyl acetate and n-hexane sub-fractions causing 24-76%, 7-75% and 5-70% reduction in fungal biomass over control, respectively. Chloroform sub-fraction with the highest antifungal potential was analyzed by GC-MS. Out of 10 compounds identified in this sub-fraction, 2H-1-benzopyran, 6,7-dimethoxy-2,2-dimethyl was the most abundant followed by hexadecanoic acid, methyl ester with peak areas of 27.58% and 18.85%, respectively. Other dominant compounds were 9,12-octadecanoic acid (Z,Z)-, methyl ester (13.67%) and 11-octadecenoic acid, methyl ester (15.28%).