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.