The inhibitory effect of vitisin B on FAS activity. A. Chemical structure of vitisin B. B. The activity for the FAS overall reaction was assayed to determine the inhibitory capability of vitisin B (0, 0.1, 0.2, 0.4, 0.6, 1.0, 2.0, 4.0 µg/ml). EGCG was chosen as a positive control to compare the inhibitory effect of vitisin B on FAS.