Antifungal metabolite from Muntingia calabura root against early leaf blight of tomato

The aim of the present study is to determine the in vitro antimicrobial activity of various extracts and fractions of Muntingia calabura (Elaeocarpaceae) root against a selected panel of microorganisms. Antifungal activity of different solvent extracts of M. calabura L. root, tested against Alternaria solani, Fusarium oxysporum f.sp. lycopersici, Pythium species, Phytophthora species, Aspergillus niger, Colletotrichum species and Rhizoctonia solani, was evaluated by agar well diffusion assay. The chromatographic fractionation of the extract resulted in the isolation of antifungal metabolite stigmasterol. The structure of the stigmasterol was confirmed using GC-MS, IR and NMR spectroscopic characterization. The stigmasterol had a potent antifungal activity with a minimum inhibitory concentration of 1 mg/ml against A. solani. Stigmasterol was subjected to docking studies carried out against fungal elicitor cryptogein. A better docking score of 12.59 with glide energy -42.56 was obtained for the complex fungal elicitor cryptogein. The interaction was done in chain A Tyr 47 [O – H…O] residue with a distance of 2.7 A°. Key words: Muntingia calabura, minimum inhibitory concentration, phytopathogens, cryptogein elicitor, stigmasterol.