Phenolic glycosides from Lindera obtusiloba and their anti-allergic inflammatory activities

Eight phenolic glycosides, tachioside (1), isotachioside (2), koaburaside (3), 2,6-dimethoxy-4-hydroxyphenyl-1-O-β-D-glucopyranoside (4), 4,6-dihydroxy-2-methoxyphenyl-1-O-β-D-glucopyranoside (5), a mixture of erigeside C (6a) and salidroside (6b), and 6-hydroxyphenyl)-1-O-β-D- glucopyranoside (7) were isolated from the stems of Lindera obtusiloba Blume. The structures of the isolates were determined by ¹H-, ¹³C-NMR, COSY, HMQC, and HMBC spectroscopy. To evaluate their anti-allergic inflammatory activities, the inhibitory effects of isolates (1-7) on histamine release and on the gene expressions of tumor necrosis factor (TNF)-α and interleukin (IL)-6 were examined using human mast cells; previous studies have reported that TNF-α and IL-6 release from mast cells is positively related to the severity of allergic symptoms. Of the tested compounds, koaburaside (3), 2,6-dimethoxy-4-hydroxyphenyl-1-O-β-D- glucopyranoside (4), and (6-hydroxyphenyl)-1-O-β-D-glucopyranoside (7) suppressed histamine release from mast cells as compared with gallic acid (positive control). In particular, 6-hydroxyphenyl)-1-O-β-D-glucopyranoside (7) attenuated the gene expressions of the proinflammatory cytokines TNF-α and IL-6 in human mast cells. Our results support the notion that phenolic glycosides isolated from L. obtusiloba inhibit mast-cell-derived allergic inflammation, histamine, and proinflammatory cytokines.