We evaluated the effect of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) on collagen synthesis in cultured human skin fibroblasts and on proliferation of fibroblasts. At concentrations of 0.1-0.5 mmol/L, AA-2G effectively stimulated collagen synthesis with an effectiveness comparable to that of L-ascorbic acid. On the other hand, 6-O-alpha-D-glucopyranosyl-L-ascorbic acid showed a weak effect. The stimulation of collagen synthesis by AA-2G was attenuated by the addition of a collagen synthesis inhibitor, L-azetidine 2-carboxylic acid, in a dose-dependent manner. In addition, AA-2G-induced stimulation of collagen synthesis could be completely inhibited by the addition of castanospermine, an inhibitor of neutral alpha-glucosidase. Relatively high alpha-glucosidase activity, which would contribute to release of ascorbic acid from AA-2G, could be detected in the lysate of cultured fibroblasts. The stimulatory activity of AA-2G on collagen synthesis was observed after 5 d in culture, whereas L-ascorbic acid tended to lose its stimulatory activity. Continuous supplementation of AA-2G (0.25 mmol/L) to culture medium for 24 d enhanced the cell growth four times that of the control. These results indicate that AA-2G is gradually cleaved by the cellular alpha-glucosidase to release L-ascorbic acid, which adequately stimulates collagen synthesis and proliferation of human skin fibroblasts.