New ethanol extraction improves the anti-obesity effects of black tea.

Black tea has been reported to have anti-obesity effects in both rodents and humans. Gallic acid, an active component of black tea, decomposes quickly into pyrogallol in high-temperature solutions. This study introduced a new, aqueous ethanol extraction of black tea, which resulted in extracts with higher concentrations of gallic acid than conventional black tea extracts prepared by hot-water extraction or hot-ethanol extraction. We confirmed that, compared with the hot-water extract of black tea, the cold-ethanol extract of black tea (CE-BTE) had greater effects on reducing body weight and body fat, improving fatty liver, regulating blood glucose, and reducing blood cholesterol in the high-fat diet-induced obese mouse model. Nonetheless, although CE-BTE significantly reduced fat content, it did not reduce peroxisome proliferator-activated receptor (PPARγ) protein in epididymal fat tissue of HFD mice. We also showed that CE-BTE did not inhibit the function of PPARγ protein to drive adipogenesis of mouse 3T3-L1 preadipocytes. Considering that PPARγ is a master transcription factor not only for adipocyte differentiation, but also for adipose tissue function, such as glucose and lipid metabolism and insulin sensitivity, these results suggest that CE-BTE reduced fat mass and body weight without dampening fat cell homeostasis and insulin sensitivity.