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

One novel C10polyacetylene rhamnoside, 4,6,8-decatriyne-1-O-α-L-rhamnopyranoside, named xylariside A (1), together with two novel C10polyacetylene 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 ofXylariasp. VDL4, an endophytic fungus isolated fromVaccinium dunalianumwight (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, andFusarium solani). Compound2demonstrated significant antifungal activities, with minimum inhibitory concentration (MIC) values ranging from 3.91 to 7.81 μg/mL. Compound2’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 againstB. cinereain 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 compound2by revealing its binding interactions with key enzyme targets inB. cinerea, thereby supporting the observed in vitro and in vivo results. Additionally, compound2showed effective inhibition of α-glucosidase, with IC50values of 5.27 ± 0.0125 μg/mL.