Flavonoids from Lindera glauca Blume as low-density lipoprotein oxidation inhibitors

In order to identify antioxidant flavonoids from Lindera glauca Blume, we performed phytochemical analysis of L. glauca Blume heartwood and isolated eight flavonoids - lindeglaucol (1), lindeglaucone (2), cilicicone B (3), tamarixetin 3-O-α-L-rhamnoside (4), procyanidin A2 (5), cinnamtannin B1 (6), cinnamtannin D1 (7), and procyanidin A1 (8) - through repeated column chromatography over silica gel (SiO₂), octadecyl silica gel (ODS) and Sephadex LH-20. The chemical structures of compounds 1-8 were elucidated from spectroscopic data (NMR, IR and MS). The low-density lipoprotein oxidation inhibitory activities of the isolated compounds were evaluated in vitro by using the thiobarbituric acid reactive substances assay. Compounds 5-8 exhibited high inhibition activity, comparable to the positive control butyl hydroxyl toluene. Compounds 2 and 3 were slightly less active, while 1 and 4 expressed low activity.