Bioactivity of a flavanol-rich lychee fruit extract in adipocytes and its effects on oxidant defense and indices of metabolic syndrome in animal models.

Many polyphenolic compounds are poorly digested, and have low bioavailability due to their long chain lengths and chemical composition. A processed, flavanol-rich lychee fruit extract (FRLFE) that is higher in flavanol monomers, dimer and trimers than its unprocessed counterpart, was tested in a variety of models. First, mature visceral adipocytes were treated with 0, 3, 10 or 30 microg/mL FRLFE (day 6-8). Compared with the controls, the treated cells had lower triglyceride concentrations, less lipid accumulation and a smaller lipid droplet size. Adiponectin release was significantly greater in cells receiving 3 or 10 microg/mL FRLFE than in the controls. Second, rats given a single dose of 50 or 100 mg/kg FRLFE had significant increases in plasma (-)-epicatechin, 3'-O-methyl-(-)-epicatechin, and (+)-catechin levels, peak values were at approximately 2 h and appreciable concentrations were still detected at 6 h. Rats supplemented daily for 1 week with 50 or 100 mg/kg FRLFE had significantly elevated metabolite concentrations. In response to an oxidative stress, erythrocyte membrane integrity was significantly improved in the 100 mg/kg FRLFE group. Third, 7-month-old mice fed a 200 mg/kg FRLFE diet for 10 months showed a significant decrease in glucose, triglyceride and lipid peroxide levels compared with mice fed a control diet. Collectively, these results support the concept that the flavanols present in FRLFE are well absorbed and bioactive.