TA is known to exhibit various health-beneficial activities (33) (34) (35) (36) . As a constituent of red wine, it has been shown to effectively reduce blood glucose levels in type 2 diabetes patients (37) and the production of endothelin-1 (38), a key protein factor intimately involved in the development of cardiovascular disease (38) . In our study, TA was found to be much more potent and efficacious than the ellagitannin Lagerstroemin (29) . Therefore, TA was chosen as the focus of our research for isolating active compounds from the tannin fraction Figure 3 . Absence of glucose transport stimulatory activity of corosolic acid in adipocytes. Pure corosolic acid in aqueous solution was added to 3T3-L1 adipocytes grown in wells of 6-well cell culture plates to induce glucose transport by a commonly used procedure (28, 29) . Cells treated with either 1 mM insulin or 30 mM penta-galloyl-glucose (PGG) were used as positive controls. Cells treated with water vehicle served as negative controls. Samples were in triplicate in the experiment, and the experiment was repeated three times. No difference was found by a one-way ANOVA statistical analysis between the negative (vehicle) control and corosolic acid samples at any concentration.