论文部分内容阅读
Objective:To investigate the phenolic composition,antioxidant properties,and hepatoprotective mechanisms of poiyphenols from green tea extract (GTP) in carbon tetrachloride (CCl4)-induced acute liver injury mouse model.Methods:High-performance liquid chromatography was used to analyze the chemical composition of the extract.Antioxidant activity of GTP was assessed by O2-,OH·,DPPH·,and ferric-reducing antioxidant power (FRAP) assay in vitro.Sixty Kunming mice were divided into 6 groups including control,model,low-,medium-,and high-doses GTP (200,400,800 mg/kg) and vitamin E (250 mg/kg) groups,10 in each group.GTP and vitamin E were administered at a level of abovementioned doses twice per day for 7 days prior to exposure to a single injection of CCl4.Hepatoprotective effects of GTP were evaluated in a CCl4-induced mouse model of acute liver injury,using commercial enzyme linked immunosorbent assay kits,histopathological observation,terminal deoxynucleotidyl transferase-mediated dUTPNick-end labeling (TUNEL) assay and Western blot.Results:GTP contained 98.56 μg gallic acid equivalents per milligram extract total polyphenols,including epicatechingallate,epigallocatechin gallate,epicatechin,and epigallocatechin.Compared with the model group,low-,medium-,or high doses GTP significantly decreased serum levels of alanine aminotransferase and aspartate transaminase (P＜0.01).Histopathological observation confirmed that pretreatment of GTP prevented swelling and necrosis in CCl4-exposed hepatocytes.Hepatoprotective effects of low-,medium-,and highdose GTP were associated with eliminating free radicals and improving superoxide dismutase,catalase,and glutathione peroxidase activity in the liver.Additionally,low-,medium-,and high-dose GTP decreased cell apoptosis in the CCl4-exposed liver (P＜0.01).Phosphorylated nuclear factor kappa-B (NF-κ B),p53,Bcl-2 associated x protein/B-cell lymphoma/leukemia-2 gene,cytochrome C,and cleaved caspase-3 levels were downregulated compared with the model group (P＜0.01).Conclusion:GTP achieves hepatoprotective effects by improving hepatic antioxidant status and preventing cell apoptosis through caspase-3-dependent signaling pathways.