Antifungal Polyacetylenic Deoxyglycosides Isolated from Endophytic Fungus Xylaria sp. VDL4 Associated with Vaccinium dunalianum.

Abstract

One novel C₁₀ polyacetylene rhamnoside, 4,6,8-decatriyne-1-O-α-L-rhamnopyranoside, named xylariside A (1), together with two novel C₁₀ polyacetylene quinovopyranosides, 4,6,8-decatriyne-1-O-α-D-quinovopyranoside, xylariside B (2), and 8E-decaene-4,6-diyne-1-O-α-D-quinovopyranoside, xylariside C (3), were obtained from the solid fermentation of Xylaria sp. VDL4, an endophytic fungus isolated from Vaccinium dunalianum wight (Ericaceae). Their chemical structures were elucidated through a combination of spectroscopic techniques. The antifungal activities of these compounds were evaluated in vitro against four phytopathogenic fungi (Fusarium oxysporum, Botrytis cinerea, Phytophthora capsici, and Fusarium solani). Compound 2 demonstrated significant antifungal activities, with minimum inhibitory concentration (MIC) values ranging from 3.91 to 7.81 μg/mL. Compound 2's effectiveness levels were similar to those of the reference drugs thiabendazole and carbendazim (each MIC = 0.98-15.62 μg/mL). Xylariside B (2) was further evaluated against B. cinerea in vivo. It exhibited remarkable efficacy in both the prevention and treatment of tomato and strawberry gray mold. Molecular docking studies confirmed the antifungal mechanism of compound 2 by revealing its binding interactions with key enzyme targets in B. cinerea, thereby supporting the observed in vitro and in vivo results. Additionally, compound 2 showed effective inhibition of α-glucosidase, with IC₅₀ values of 5.27 ± 0.0125 μg/mL.