Structural characterization, in-silico studies, and antifungal activity of 5-methylmellein isolated from endophytic Alternaria burnsii.

Abstract

The present investigation focused on exploring the potential of fungal endophytes as a valuable source of bioactive compounds with diverse applications. The phenolic compound 5-methylmellein was isolated for the first time from Alternaria burnsii, an endophytic fungus associated with Morus alba Linn. The compounds were structurally characterized using comprehensive spectral analysis, including ¹H-, ¹³C, and 2D-NMR, as well as HRESI-MS. The study investigated the antifungal activity of 5-methylmellein against several plant pathogenic fungi, including Botrytis cinerea, Colletotrichum gloeosporioides, Cercospora beticola, and Rhizoctonia solani. In vitro assays showed significant inhibition of various plant pathogenic fungi, and the IC₅₀ values ranging from 34.59 ± 1.03^a µg/mL to 44.76 ± 1.03^b µg/mL against the tested fungi. In vivo experiments on apples and grapes revealed that 5-Methylmellein significantly reduced fruit decay caused by Botrytis cinerea. The wound incidence in the control group reached 95.78%, while the treated groups exhibited a reduction of 37.54% after 15 days. These findings underscore the potential of 5-methylmellein as a potent antifungal agent, suggesting its eco-friendly application in agriculture for managing fruit decay.