Analysis of chemical composition in Chinese olive leaf tea by UHPLC-DAD-Q-TOF-MS/MS and GC-MS and its lipid-lowering effects on the obese mice induced by high-fat diet.

In the present study, the chemical constituents and inhibitory effects of Chinese olive leaf tea (OLT) on α-amylase, α-glucosidase, and its lipid-lowering effects on obese mice induced by a high fat diet were evaluated. In total, 17 compounds including hydroxytyrosol, hydroxytyrosol-glucoside were tentatively identified as main compounds of OLT with authentic compounds or referring to published articles and accessible databases. In total 105 volatile compounds were identified, in which hexanal, benzaldehyde and nonanal were the main aroma compounds. The bioassay showed that the IC50 values of the OLT on α-amylase and α-glucosidase were 0.2102 g/mL and 2.925 mg/mL, respectively. It also indicated that the OLT is effective in improving the glucose homeostasis by oral starch tolerance test (OSTT). The experimental results in vivo also indicated that OLT significantly improved body weight, liver weight, abdominal fat, plasma levels of lipids, hepatic and plasma malondialdehyde (MDA) levels compared with obese mice fed high-fat diet. The OLT can enhance the antioxidant enzymes' activities (SOD and GSH-Px), meanwhile prevent the hepatic inflammation induced by high-fat diet. In summary, OLT has a potential application in preventing metabolic syndromes.