Phthalate-related metabolites from an endophytic Alternaria sp. YUD24001 associated with Aconitum hemsleyanum

Seven undescribed phthalate-related compounds, designated alternyxtiols A-G (1-7), were isolated from the endophytic fungus Alternaria sp. YUD24001, which was found in Aconitum hemsleyanum. The structures of alternyxtiols A and B feature a benzofuran ring instead of the typical benzofuran ketone structure. Alternyxtiol C is identified as a penta-substituted phenol derivative, whereas alternyxtiols D-G comprise two rare penta-substituted phenol dimers. The chemical structures of these compounds were elucidated through spectral data analysis. Their absolute configurations were determined using TDDFT-ECD calculations and DP4+ probability analysis, which relied on NMR chemical shift calculations. Notably, the structures of alternyxtiols F and G possess highly functionalized penta-substituted benzene ring cores, differing from other benzene ring dimer compounds in their alkyl substitution patterns. Alternyxtiols B, F and G exhibited antimicrobial activity against pathogenic fungi Fusarium solani, Alternaria panax and Epicoccus nigrum, respectively.