Protective effect of hypoxylonol C and 4,5,4′,5′-tetrahydroxy-1,1′-binaphthyl isolated from Annulohypoxylon annulatum against streptozotocin-induced damage in INS-1 cells

[Display omitted] •Annulohypoxylon annulatum compounds protect INS-1 cell damage by STZ.•A. annulatum compounds prevented apoptosis.•Hypoxylonol C and BNT are active compounds of A. annulatum. We evaluated the protective effects of hypoxylonol C and 4,5,4′,5′-tetrahydroxy-1,1′-binaphthyl (BNT) isolated from Annulohypoxylon annulatum on pancreatic β-cell apoptosis, using the β-cell toxin streptozotocin (STZ). Hypoxylonol C and BNT restored the STZ-induced decrease in INS-1 cell viability in a dose-dependent manner. In addition, treatment of INS-1 cells with 50 μM STZ resulted in an increase in apoptotic cell death, which was observed as annexin V fluorescence intensity. Apoptotic cell death was decreased by co-treatment with 100 μM hypoxylonol C and 100 μM BNT. Similarly, STZ caused a marked increase in the expression of cleaved caspase-8, caspase-3, Bax, and poly (ADP-ribose) polymerase (PARP), as well as a decrease in the expression of B-cell lymphoma 2 (Bcl-2), which was reversed by co-treatment with 100 μM hypoxylonol C and 100 μM BNT. These findings suggest that hypoxylonol C and BNT play an important role in protecting pancreatic β-cells against apoptotic damage.