Xanthones with α‐Glucosidase Inhibitory Activities from Aspergillus versicolor, a Fungal Endophyte of Huperzia serrata

Three new xanthones, namely huperxanthones A–C (1–3, resp.), were obtained from the cultures of Aspergillus versicolor, a fungal endophyte of Huperzia serrata, together with 1,7-dihydroxy-8-(methoxycarbonyl)xanthone-3-carboxylic acid (4), β-diversonolic acid methyl ester (5), 4-hydroxyvertixanthone (6), and sydowinin B (7). The structures of the new compounds were established by detailed NMR and MS analysis, especially by 2D-NMR experiments. All xanthones were evaluated for their effects on α-glucosidase. Compound 4 exhibited a potent inhibitory activity against α-glucosidase with an IC50 value of 0.24 mM (vs. 0.38 mM for acarbose). The rest of the compounds showed weak or no activity against α-glucosidase.