Antifungal and antimycotoxigenic potency of Solanum torvum Swartz. leaf extract: isolation and identification of compound active against mycotoxigenic strains of Aspergillus flavus and Fusarium verticillioides.

Abstract

The main objective of this study was to investigate the antifungal effect of Solanum torvum leaves against different field and storage fungi, and to identify its active compound. In addition, to evaluate invitro and invivo inhibitory efficacy on toxigenic strains of Aspergillus flavus and Fusarium verticillioides. Leaves of S.torvum were sequentially extracted with petroleum ether, toluene, chloroform, methanol and ethanol. The antifungal compound isolated from chloroform extract was identified as torvoside K based on spectral analysis. The antifungal activity of chloroform extract and torvoside K was determined by broth microdilution and poisoned food techniques. The minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC) and zone of inhibition (ZOI) were recorded. Further, inhibitory effects of chloroform extract and torvoside K on growth of A.flavus and F.verticillioides, and their toxin productions were evaluated using invitro and invivo assays. Torvoside K showed the significant activity against tested fungi with ZOIs and MICs ranging from 33·4 to 87·4% and 31·25-250μgml(-1) , respectively. Further, torvoside K showed concentration-dependent antimycotoxigenic activity against aflatoxin B1 and fumonisin B1 production by A.flavus and F.verticillioides, respectively. It was observed that the compound torvoside K significantly inhibited the growth of all fungi tested. Growth of A.flavus and F.verticillioides, and aflatoxin B1 and fumonisin B1 productions were completely inhibited invitro and invivo by torvoside K with increasing concentration. Control of mycotoxigenic fungi requires compounds that able to inhibit both fungal growth and mycotoxin production. The antimycotoxigenic potential of torvoside K of S.torvum is described in this study for the first time. The results indicate the possible use of S.torvum as source of antifungal agents against postharvest fungal infestation of food commodities and mycotoxin contaminations.