Anti-inflammatory activities of compounds from twigs of Morus alba

•Five new compounds (1-5) were isolated from Morus alba.•Thirty one known compounds (6-36) were also isolated.•Compounds 1, 17, 25-28, and 32 showed the inhibitory of NO production.•Compounds 1, 2, 17, 25, and 32 inhibited the iNOS activities in LPS stimulated RAW 264.7 cells.•Compounds 1, 17, and 32 were significantly active on COX-2 induction.

Five new compounds, 10-oxomornigrol F (1), (7″R)-(−)-6-(7″-hydroxy-3″,8″-dimethyl-2″,8″-octadien-1″-yl)apigenin (2), ramumorin A (3), ramumorin B (4), and (4S,7S,8R)-trihydroxyoctadeca-5Z-enoic acid (5), together with 31 known compounds (6-36), were isolated from the twigs of Morus alba (Moraceae). The chemical structures of these compounds were established using spectroscopic analyses, 1D and 2D NMR, high-resolution electrospray ionization mass spectrometry (HRESIMS), and Mosher's methods. The anti-inflammatory activities of the compounds were evaluated by investigating their ability to inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) production in macrophage RAW 264.7 cells. Compounds 1, 2, 13, 17, 19, 25-28, and 32 showed inhibitory effects with IC50 values ranging from 2.2 to 5.3 μg/mL. Compounds 1, 2, 17, 25, and 32 reduced LPS-induced inducible nitric oxide synthase (iNOS) expression in a concentration-dependent manner. In addition, pretreating the cells with compound 1, 17, and 32 significantly suppressed LPS-induced expression of cyclooxygenase-2 (COX-2) protein.

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