In vitro antioxidant and lipid-lowering properties of free and bound phenolic compounds from buckwheat hulls

Polyphenols can perform preventive and alleviating functions in many metabolic disorders. Buckwheat hulls, usually discarded as waste, are known to have plenty of phenolic compounds. The present study aimed to explore the composition and in vitro lipid-lowering and antioxidant activities of the free and bound phenolic compounds (FPBH and BPBH) in buckwheat hulls. The contents of phenolic compounds in FPBH and BPBH were 150.25 +/- 6.25 mg g(-1) and 44.25 mg g(-1) respectively, indicating that free phenols were the main form of phenols in buckwheat hulls. Rutin and syringic acid was the most abundant phenolic compounds in FPBH and BPBH respectively. The results of DPPH and ABTS free radical scavenging ability showed that the antioxidant activity of FPBH was significantly higher than that of BPBH. In vitro assessments showed that both FPBH and BPBH could significantly alleviate lipid accumulation and oxidative stress in oleic acid (OA)-treated HepG(2) cells with a dose-dependent manner by decreasing the levels of intracellular ROS, mitochondrial membrane potential (MMP), triglyceride (TG), total cholesterol (TC) and low density lipoprotein (LDL-C) as well as significantly improving intracellular total antioxidant capacity (TAC), the levels of high density lipoprotein (HDL-C) and activities of glutathione peroxidase. (GSH-Px), superoxide dismutase (SOD) and catalase (CAT). Meanwhile, FPBH was more effective than BPBH at the same concentration. It was concluded that phenolic compounds in buckwheat hulls might have great potential to develop functional foods in improving oxidative damage and lipid metabolism disorders.