Staprexanthones, Xanthone-Type Stimulators of Pancreatic β-Cell Proliferation from a Mangrove Endophytic Fungus

This project was focused on the discovery of novel compounds that promote endogenous beta-cell regeneration. Screening of extracts identified the fungus Stachybotrys chartarum as a promising candidate. After fermentation and extraction of S. chartarum, we isolated five new prenylated xanthones, namely, staprexanthones A-E (1-5), with staprexanthone A (1) being the first natural xanthone bearing a rare 4,5-dimethyl-1,3-dioxolane moiety. Compounds 1, 2, and 5 significantly increased beta-cell numbers in vivo in a zebrafish model. Further analysis revealed that 2 and 5 promoted beta-cell mass expansion by increasing proliferation of existing beta-cells though promotion of cell-cycle progression at the G1/S transition. These findings indicate that prenylated xanthones are potential new drug leads for antidiabetes therapy by stimulating beta-cell regeneration.