Intramolecular acyl migration and enzymatic hydrolysis of a novel monoacylated ascorbic acid derivative, 6-O-dodecanoyl-2-O-alpha-d-glucopyranosyl-L-ascorbic acid.

A stable ascorbic acid derivative, 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G), exhibits vitamin C activity in vitro and in vivo after enzymatic hydrolysis to ascorbic acid. AA-2G has been approved by the Japanese Government as a quasi-drug principal ingredient in skin care and as a food additive. In order to achieve efficient action as an ascorbic acid source, a pro-vitamin C agent, on a variety of cells or tissues, we have synthesized a series of monoacyl AA-2G derivatives. Our previous studies indicate that a series of the derivatives is a readily available source of AA activity in vitro and in vivo, and suggested that intramolecular acyl migration of the derivatives might have occurred in a neutral aqueous solution. In this study, intramolecular acyl migration and enzymatic hydrolysis of a monoacyl AA-2G derivative, 6-O-dodecanoyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acid (6-sDode-AA-2G), were investigated. 6-sDode-AA-2G underwent an intramolecular acyl migration to yield ca. 10% of an isomer in neutral aqueous solutions, and the acyl-migrated isomer was isolated and characterized as 5-O-dodecanoyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acid (5-sDode-AA-2G). In some tissue homogenates from guinea pigs as well as in neutral aqueous solutions, 6-sDode-AA-2G underwent partial acyl migration to give 5-sDode-AA-2G. 6-sDode-AA-2G and the resulting 5-sDode-AA-2G were predominantly hydrolyzed with esterase to AA-2G and then with alpha-glucosidase to ascorbic acid in the tissue homogenates. The results will provide a further basis for its use as an ingredient in skin care, as an effective pharmacological agent and as a promising food additive.