l-Ascorbic Acid Biosynthesis in Higher Plants from l-Gulono-1, 4-lactone and l-Galactono-1, 4-lactone

Detached bean (Phaseolus vulgaris) and strawberry (Fragaria) fruits fed l-gulono-1,4-lactone or l-galactono-1,4-lactone convert this compound, in part, to l-ascorbic acid. When l-galactono-1,4-lactone is given as a 0.25% solution to detached bean shoots, the ascorbic acid content is tripled in less than 10 hours. l-Gulono-1,4-lactone is only 5 to 10% as effective as its epimer. Experiments with specifically labeled l-gulono-1,4-lactone and l-galactono-1,4-lactone prove that conversion is direct. Ascorbic acid is labeled at the same carbon as its precursor.A method is described for preparation of l-galactono-1,4-lactone-2-(14)C from myo-inositol-2-(14)C. This method can be extended to the preparation of l-ascorbic acid-2-(14)C on the basis of results obtained in the present study.