Eighteen secondary metabolites were isolated from the fermentation broth of the endophytic fungus Xylaria sp. SYPF 8246, including four new compounds, xylarianins A-D (1-4), three new natural products, 6-methoxycarbonyl-2'-methyl-3,5,4',6'-tetramethoxy-diphenyl ether (5), 2-chlor-6-methoxycarbonyl-2'-rnethyl-3,5,4',6'-tetramethoxy-diphenyl ether (6), and 2-chlor-4'-hydroxy-6-methoxy carbonyl-2'-methyl-3,5,6'-trimethoxy-diphenyl ether (7), and eleven known compounds (8-18). Their structural elucidations were conducted by using 1D and 2D NMR, HRESIMS, and Rh2(OCOCF3)4-induced electronic circular dichroism (ECD) spectra analyses. The integrated 1H and 13C NMR data of three new natural products 5-7 were reported for the first time. All the isolated compounds were assayed for their inhibitory activities against human carboxylesterase 2 (hCE 2). Compounds 1, 5-9, and 18 displayed significant inhibitory activities against hCE 2 with IC50 values of 10.43 ± 0.51, 6.69 ± 0.85, 12.36 ± 1.27, 18.25 ± 1.78, 29.78 ± 0.48, 18.86 ± 1.87, and 20.72 ± 1.51 µM, respectively. The interactions between compounds 1 and 5 with hCE 2 were anaylzed by molecular docking.
Keywords: Endophytic fungus; Inhibitory hCE 2 activity; Molecular docking; Secondary metabolites; Xylaria sp. SYPF 8246.
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