Determination of total phenols and flavonoids, antioxidant potential and antimicrobial activity of hydroalcoholic extract of Withania somnifera against fungi cause spoilage postharvest apple and strawberry fruits

In the present study, the hydroalcoholic extract of Withania somnifera was extracted and then the content of total phenol (by Folin-Ciocalteu reagent), total flavonoid (by aluminum chloride method), antioxidant activity (based on DPPH and ABTS free radical scavenging methods) and its antifungal effect against Rhizopu stolonifers, Botrytis cinerea, Penicillium expansum and Alternaria alternata (fungi cause spoilage postharvest apple and strawberry fruits) were determined based on disk diffusion agar, well diffusion agar, minimum inhibitory concentration, and minimum fungicidal concentration. The amount of phenol and flavonoids in the extract was 53.16 mg GAE/g and 28.20 mg QE/g, respectively. The antioxidant power of the hydroalcoholic extract was 69.80 and 57.15 μg/ml in terms of DPPH and ABTS free radical scavenging, respectively. The results of antimicrobial activity based on disk diffusion agar and well diffusion agar showed that increasing the concentration of the extract caused a significant increase in the diameter of the growth inhibition zone and Botrytis cinerea and Alternaria alternata were the most resistant and sensitive strains to the extract, respectively. In general, Penicillium expansum and Alternaria alternata were more sensitive than Rhizopus stolonifer and Botrytis cinerea with minimum inhibitory and fungicidal concentrations of 16 and 128 mg/ml, respectively.