In vitro antioxidant properties and in vivo lowering blood lipid of Forsythia suspense leaves

The active compounds from Forsythia suspense were screened for antioxidant activities in vitro and lowering blood lipid and lipid peroxidation in vivo. Five compounds, ursolic acid, phillygenin, (+)-pinoresinol, and quercetin, from EtOAC extract and rutin from n-BuOH extract were isolated and identified by spectroscopic methods. Phillygenin and (+)-pinoresinol had notable scavenging activity against DPPH, ABTS radicals, as well as potent reducing power in FRAP assay in vitro. Intragastric administration of EtOAC extract (500 mg/kg body weight per day), ursolic acid (150 mg/kg), phillygenin (150 mg/kg), and rutin (70 mg/kg) to groups of hyperlipidemia mice for 10 days significantly decreased the level of blood triglyceride and the level of low-density lipoprotein cholesterol (P < 0.001) in serum. However, the level of blood high-density lipoprotein cholesterol in the same treated mice decreased slightly (P > 0.05). The level of hepatic malondialdehyde (MDA, an index of lipid peroxidation) was assayed to evaluate the mechanism(s) of EtOAC extract, ursolic acid, phillygenin, and rutin. Under hyperlipidemia condition, the level of hepatic MDA increased. After intragastric administration of EtOAC extract, ursolic acid, phillygenin, and rutin, the level of hepatic MDA significantly decreased. The result showed that EtOAC extract, ursolic acid, phillygenin, and rutin had a high hypolipidemic activity and this activity may be attributed to their antioxidant potential.