Bioavailability of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid as ascorbic acid in healthy humans.

2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA2G) is a stable glycoside, but its conversion to bioavailable ascorbic acid (AsA) in humans remains unknown. The aim of this study was to clarify that AA2G is hydrolyzed by human intestinal maltase and AA2G by oral ingestion is physiologically utilized the same as AsA in human subjects. The hydrolyzing activities to AA2G by human or rat intestinal homogenates were measured by high-performance liquid chromatography. In a human experiment eight healthy female subjects (23.5 +/- 0.5 y old, body mass index 20.1 +/- 0.7 kg/m(2)) ingested 3.84 g of AA2G (equivalent to 2 g of AsA) and 2 g of AsA. Blood was collected 0, 1, 2, 3, and 4 h after ingestion. The concentrations of serum AsA were compared with those of rats administered 76.8 mg of AA2G (equivalent to 40 mg of AsA). AA2G was hydrolyzed by maltase using human intestinal homogenate the same as that of rat. When AA2G was orally administered to human subjects, the changed value of the serum concentration of AsA was 1.6 mg/100 mL from baseline at 2 h and then maintained until 4 h after administration. These concentrations were not significantly different from those after ingestion of AsA. In the case of rat, the AsA concentrations in serum were linearly increased to 1.7 mg/100 mL until 3 h after administration. AA2G is hydrolyzed by intestinal maltase and acts as AsA in humans. The present results will contribute to the development of functional food with health claims to supply AsA.