Bioavailability of a Series of Novel Acylated Ascorbic Acid Derivatives, 6-O-Acyl-2-O-α-D-glucopyranosyl-L-ascorbic Acids, as an Ascorbic Acid

The bioavailability of a series of novel acylated ascorbic acid derivatives, 6-O-acyl-2-O-α-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G), as an ascorbic acid (AA) supplement was investigated in rats and guinea pigs. Oral administration of 6-Acyl-AA-2G to rats resulted in an increase in the plasma AA level. However, the intact form was not detectable in the plasma by high-performance liquid chromatography, indicating its hydrolysis through the process of absorption. After an intravenous injection to rats of 6-Octa-AA-2G as a representative derivative, the intact form rapidly disappeared from the plasma, being followed by a prolonged and marked elevation of the plasma AA level. Various tissue homogenates from guinea pigs were examined for their releasing activity of AA, 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) and 6-O-acyl-AA from 6-Acyl-AA-2G. High activity was observed in the small intestine. These hydrolytic activities to AA and 6-O-acyl-AA were completely inhibited by castanospermine, an α-glucosidase inhibitor, and AA-2G was observed as the only resulting hydrolysate, suggesting the participation of α-glucosidase and esterase in the in vivo hydrolysis of 6-Acyl-AA-2G. 6-Octa-AA-2G was found to exhibit an obvious therapeutic effect in scorbutic guinea pigs from its repeated oral administration. These results indicate that 6-Acyl-AA-2G is a readily available source of AA activity in vivo, and may be useful as an effective pharmacological agent and as a promising food additive.