Two New Compounds Isolated From the Endophytic Fungus <i>Guignardia Mangiferae</i> VDL166 of <i>Vaccinium Dunalianum</i>

ABSTRACT 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 c omputed 13 C 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.