Two New Compounds Isolated From the Endophytic Fungus Guignardia Mangiferae VDL166 of Vaccinium Dunalianum

Two structurally new benzene derivatives, designated as Guignarphenyl A (1) and Guignarphenyl B (2), and one structurally unique meroterpenoid named Guignarpenoid A (6) were successfully isolated and identified from the solid fermentation products of the endophytic fungus Guignardia mangiferae strain VDL166 (derived from Vaccinium dunalianum Wight, Ericaceae). Among these new compounds, compound 1 is reported for the first time in nature, while compounds 2 and 6 are newly identified analogs. Additionally, thirteen known secondary metabolites (3-5, 7-16) were obtained. The structures of all compounds were elucidated by comprehensive nuclear magnetic resonance (NMR) spectroscopic analysis combined with computed ¹³C NMR chemical shift analysis and DP4+ probability analysis for key relative configurations, and electronic circular dichroism (ECD) calculations. All isolates were evaluated for their in vitro antifungal activities against four phytopathogenic fungi (Alternaria brassicicola, Botrytis cinerea, Phytophthora infestans, and Valsa mali). Among them, compound 6 exhibited the most potent and broad-spectrum activity with MICs ranging from 12.5 to 25.0 µg/mL, comparable to the positive controls (Carbendazim and Thiabendazole). SUMMARY: Two new benzene derivatives, guignarphenyl A (1) and guignarphenyl B (2), and a novel meroterpenoid, guignarpenoid A (6), were isolated from Guignardia mangiferae VDL166. Structures were elucidated by NMR, ECD calculations, and DP4+ probability analysis. Compound 6 showed potent broad-spectrum antifungal activity (MICs 12.5-25.0 µg/mL). Bioactivity-guided study confirms the antifungal potential of G. mangiferae metabolites.