Bioassays Guided Fractionation of Ageratum conyzoides Extract for the Identification of Natural Antifungal Compounds against Macrophomina phaseolina

Abstract

Macrophomina phaseolina (Tassi) Goid. 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 billygoat-weed (Ageratum conyzoides L.) through bioassays guided fractionation for the control of M. phaseolina. Extracts of different parts of the weed were made in methanol and antifungal bioassays were conducted using 1, 2, 3, 4 and 5% concentrations 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 namely n-hexane, chloroform, ethyl acetate and n-butanol. Bioassays carried out with different concentrations (3.125, 6.25, 12.5, 25, 50, 100 and 200 mg mL-1) of the sub-fractions of stem extract revealed the highest antifungal potential of chloroform sub-fraction with 56–93% reduction in the 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, 7-dimethoxy-2,2-dimethyl- (27.58%) was the most abundant followed by hexadecanoic acid, methyl ester (18.85%); 11-octadecenoic acid, methyl ester (15.28%) and 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester (10.88%), which could be responsible for antifungal activity. © 2021 Friends Science Publishers