Three new lignan glycosides with IL-6 inhibitory activity from Akebia quinata

Three new lignan glycosides, akeqintoside A [(7S,8S)-7,8-dihydro-8-hydroxymethyl-7-(4-hydroxy-3-methoxyphenyl)-1'-benzofuranpropanol 2'-O-β-D-glucopyranoside] (1), akeqintoside B [(7R,8R)-7,8-dihydro-8-hydroxymethyl-7-(4-hydroxy-3-methoxyphenyl)-1'-(9'-methoxy-7'-propenyl) benzofuran 2'-O-β-D-glucopyranoside] (2), and akequintoside C [7R*,8R*-dihydroxy-7-(4-hydroxy-3-methoxyphenyl)-glycerol 9-O-β-D-(6'-O-caffeoyl)-glucopyranoside] (3) were isolated from Akebia quinata along with five known compounds, syringin (4), vanilloloside (5), salidroside (6), 3,4-dihydroxyphenylethyl alcohol 8-O-β-D-glucopyranoside (7), and calceolarioside B (8). The structures of the compounds were identified based on one dimensional (1D)- and 2D-NMR, including (1)H-(1)H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser effect spectroscopy (NOESY) spectroscopic analyses. The inhibitory activity of these isolated compounds against interleukin-6 (IL-6) production in tumor necrosis factor-alpha (TNF-α) stimulated MG-63 cells was also examined.