PREPARATION AND ANTIOXIDANT ACTIVITIES OF PHENOLIC ESTERS AND ETHERS OF L-ASCORBIC-ACID

Esterification of L-ascorbic acid in concentrated sulfuric acid with 0 .33 moles of gallic acid gave a 90% yield of a 2:5 mixture of L-ascorb yl 5- and 6-gallate esters. The 6-gallate ester (1) was purified from the 5-gallate ester (2) by fractional crystallization in 40% yield. Th ree other aromatic derivatives of L-ascorbic acid also were prepared. The order of antioxidant activities of the L-ascorbyl derivatives dete rmined by thiobarbituric acid number in methyl linolenate at 37 degree s C was as follows: 6-gallate (1) > 6-(3',4'-dihydroxy)benzoate (3) ap proximate to 6-(4'-hydroxy)phenyl ether (4) >6-(4 methoxy)phenyl ether (5).