Xylarcurcosides A-C, three novel isopimarane-type diterpene glycosides from Xylaria curta YSJ-5

Three previously undescribed isopimarane-type diterpene glycosides named as xylarcurcosides A-C (1-3) along with two known ones 16-α-d-mannopyranosyloxyisopimar-7-en-19-oic acid (4) and hypoxylonoid A (5) were successfully isolated from an ethyl acetate extract of the endophytic fungus Xylaria curta YSJ-5 growing in leaves of Alpinia zerumbet. The spectroscopic methods, electronic circular dichroism (ECD) calculations, and X-ray diffraction experiments were conducted to identify their absolute chemical structures. All these compounds were tested for in vitro cytotoxic, anti-inflammatory, α-glucosidase inhibitory, and antibacterial activities. As a result, these novel compounds demonstrated no obvious cytotoxic and antibacterial activity.