Characterization of Antifungal Metabolites of Chaetomium globosum Kunze and their Antagonism against Fungal Plant Pathogens

Abstract

Chaetomium species which are normally found in soil and organic compost are noted for the presence of secondary metabolite with biological activities. Secondary metabolites from culture filtrate of Chaetomium globosum Kunze were extracted by solvent extraction method using ethyl acetate and separated by thin layer chromatography in five major bands of different R_f values. These compounds were further purified and fractioned with column chromatography. Compound '1' eluted with hexane (fraction 1-18) as color less liquid (R_f 0.84), and other five compounds (2,3,4,5,6) with different ratio of hexane, benzene and acetone as solvent in different fractions as: 34-63 (R_f. 0.46), 71-75 (R_f 0.31), 78 (R_f 0.58), 76-77 (R_f 0.58) and 85-89 (R_f 0.47) were eluted and purified. GS-MS and NMR studies revealed that compounds 2-6 were identical to spectral data of metabolites, chaetomin, BHT, mollicelin G, isomer of mollicelin G and cochiliodinol respectively. One more elution with benzene: acetone (95 : 5 v/v) gave a pale yellow crystalline compound of R_f 0.37 identified as chaetoglobosin. Bioassay studies with two compounds i.e., chaetoglobosin and chaetomin revealed significant growth inhibitory activity against various plant pathogens such as Bipolaris sorokiniana, Macrophomina phaseolina, Rhizoctonia solani and Pythium ultimum under in vitro conditions.