Sesquiterpenes and α-pyrones from an endophytic fungus Xylaria curta YSJ-5.

Chemical investigation of the culture extract of an endophyte Xylaria curta YSJ-5 from Alpinia zerumbet (Pers.) Burtt. et Smith resulted in the isolation of eight previously undescribed compounds including five eremophilane sesquiterpenes xylarcurenes A-E, one norsesquiterpene xylarcurene F, and two α-pyrone derivatives xylarpyrones A-B together with eight known related derivatives. Their chemical structures were extensively established based on the 1D- and 2D-NMR spectroscopic analysis, modified Mosher's method, electronic circular dichroism calculations, single-crystal X-ray diffraction experiments, and the comparison with previous literature data. All these compounds were tested for in vitro cytotoxic, anti-inflammatory, α-glucosidase inhibitory, and antibacterial activities. As a result, 6-pentyl-4-methoxy-pyran-2-one was disclosed to display significant antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus with minimal inhibitory concentration value of 6.3 µg/mL.

Phomopamide A, a cyclic pentadepsipeptide with α-glucosidase inhibition activity from the endophytic fungus Diaporthe sp.

An undescribed cytotoxic cyclopeptide named phomopamide A (1) was isolated from Diaporthe sp., which is an endophytic fungus from Artemisia argyi. Phomopamide A (1) featured an pentadepsipeptide skeleton and composed of two Phe, one Val, one Leu, and one 2-hydroxyoctanoic acid units. The structure of this new compound was fully characterised on the basis of extensive spectroscopic analysis. Moreover, phomopamide A was evaluated for in vitro cyctotoxic and α-glucosidase inhibitory activity. As a result, phomopaminde A exhibited no cytotoxic activity against four tumour cell lines, while it showed a potent α-glucosidase inhibition effect with IC50 value of 62.35 µM.

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.