Phenolic constituents from the flower buds of Lonicera japonica and their 5-lipoxygenase inhibitory activities

Thirteen phenolic constituents, luteolin (1), protocatechuic acid (2), caffeic acid (3), flavoyadorinin-B (4), 4,5-dicaffeoylquinic acid (5), luteolin 7-O-β-d-glucopyranoside (7), 3,5-dicaffeoylquinic acid methyl ester (8), methyl chlorogenate (9), quercetin 3-O-β-d-glucopyranoside (10), 3,5-dicaffeoylquinic acid (11), rhoifolin (12), chlorogenic acid (13), and a novel phenolic glucoside benzoate, vanillic acid 4-O-β-d-(6-O-benzoylglucopyranoside) (6), were isolated from the flower buds of Lonicera japonica. Flavoyadorinin-B (4) was isolated for the first time from a Caprifoliaceae plant. The structures of 1–13 were determined on the basis of chemical and spectroscopic evidence. These compounds were screened for their 5-lipoxygenase inhibitory activity. Only luteolin (1) showed significant inhibitory activity against 5-LOX-catalysed leukotriene production.