Isoindolinone-containing meroterpenoids with α-glucosidase inhibitory activity from mushroom Hericium caput-medusae

Hericium caput-medusae is an edible and medicinal mushroom closely relative to H. erinaceus. According to our detailed chemical investigation, two novel isoindolinone-containing meroterpene dimers, caputmedusins A (1) and B (2), as well as nine analogues, caputmedusins C-K (3-11), were isolated from the fermentation broth of H. caput-medusae. Their structures were elucidated by analyses of 1D and 2D NMR spectroscopic methods. The absolute configurations of 1-4 were speculated based on the specific optical rotation and biogenetic consideration. The absolute configurations of 10 and 11 were rationalized by the calculation of ¹H NMR chemical shifts. Caputmedusins A-C (1-3) showed moderate inhibitory activity against α-glucosidase with the IC₅₀ values of 39.2, 36.2 and 40.8μM, respectively.