Molecular modification of proanthocyanidins.

Regioselective enzymatic acylation of proanthocyanidin is proposed and investigated as a method by which to improve the solubility of proanthocyanidins in the oil phase and maintain its oxidation resistance. Experimental results indicate that butanol functions as the best solvent in the studied reaction, in which Lipase Novozym435 is used as biological catalyst enzyme and the molar ratio of lauric acid to proanthocyanidins is 4:1. To increase the esterification conversion, we propose the addition of molecular sieve at 5 h. The product was separated by TLC, and results indicate an optimal solvent ratio of ethyl acetate: petroleum ether: acetic acid = 2:3:0.5. This condition can effectively separate the ester and proanthocyanidins, achieving an esterification yield of 60.9%.