Characterization of Hypolipidemic Phenol Analogues from Fermented Tea by Eurotium cristatum

Fuzhuan brick tea (FBT), a type of black tea, is a traditional beverage in China, especially popular among frontier ethnic groups. FBT is well-known for its health benefits, such as hypoglycemic, anti-hypertensive, anti-inflammatory, diuretic, and detoxification effects. Nevertheless, the underlying mechanisms on the molecular level are still elusive and the key compounds responsible for the health benefits are unidentified. Previous studies have mainly focused on functional studies of the water extract. However, FBT is typically cooked with butter or milk. Therefore, we hypothesized that some lipophilic components in FBT, which can be absorbed through the co-consumption of butter or milk, may play an important role in the health benefits. The present study aimed to investigate whether the liposoluble extract of FBT alleviates symptoms related to metabolic diseases and to identify the active compounds involved. By comparing the high-performance liquid chromatography (HPLC) profiles of water, milk and hexane extract, some low polarity peaks were observed in the milk and hexane extracts. Furthermore, the hexane extract treatment alleviated body weight gain, serum total cholesterol and triglyceride levels, and inhibited the accumulation of hepatic fat granules in a high-fat diet (HFD)-induced C57BL/6N mouse model. In order to identify the key functional lipophilic compounds in FBT, the hexane extract of FBT was subjected to chemical characterization. Four phenol analogs were characterized, namely, isodihydroauroglaucin (1), dihydroauroglaucin (2), tetrahydroauroglaucin (3), and flavoglaucin (4). Compounds 1 and 4 reduced the levels of total cholesterol and triglyceride in vivo. Both compounds also inhibited the high-fat diet-induced body weight gain and accumulation of fat granules in the liver of C57BL/6N mice. Isodihydroauroglaucin and flavoglaucin have therefore been identified as bioactive ingredients that contribute to the health benefits of FBT.