Catechin inhibits glycosidases, ameliorates glucose uptake and Glut-4 expression in 3T3-L1 adipocytes

The research aimed to determine the inhibitory effects of different fractions of Camellia sinensis on α-glucosidase, α-amylase, glucose uptake, and Glut-4 expression in 3T3-L1 adipocytes and identification of the active principle. The crude aqueous extract was sequentially sub-fractionated using preparative HPLC and subjected to in vitro assays. Fraction 1 (F1) exhibited effective inhibition of both α-glucosidase and α-amylase with an IC₅₀ value of 90.31 µg/mL and 112.82 µg/mL, respectively. Sub-fraction 5 (F5) effectively inhibited α-glucosidase (IC₅₀ = 37.86 µg/mL) compared to acarbose (IC₅₀ = 76.19 µg/mL). The glucose uptake was significantly increased to 1.5 (p < 0.05) and 2.5-fold (p < 0.05) by F5 at 50 and 100 µM concentration, respectively. The synergistic effect of F1 to enhance glucose uptake (1.15 and 1.5-fold stimulation) was significantly higher than the control but less effective than F5. Furthermore, structure elucidation of the principle present in F5 revealed the presence of (2 R,3S)-2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol.