Preparation of esculin acetates through transesterification reaction catalyzed by Novozyme 435 ^® and their Purification followed by NMR characterization

In this study, biocatalytic transesterification reaction using Novozyme 435^® (N435) lipase was employed to enhance the hydrophobicity of esculin, aiming to improve its solubility for commercial applications and enhance its bioactivity and oral viability. The acylation reaction of esculin with vinyl acetate was conducted at 60 °C and 200 rpm for 24 h. After chromatographic and spectroscopic analysis, two products were identified: the first one was monoacylated at the 6'-OH position of the glucosyl moiety of esculin (T_R: 10.3 min and <i>m/z</i> 382.93 [M + H]⁺), and the second one was diacylated at the 6'-OH and 3'-OH positions (T_R: 13.0 min and <i>m/z</i> 424.93 [M + H]⁺). The latter was the major product, with a conversion rate of 53.550 ± 0.368%, while the monoacetylated one showed 8.715 ± 0.064%. Both products were isolated by high-speed counter-current chromatography (HSCCC) using a two-phase system HEMWat 1:9:1:9 and characterized by NMR. In this way, these results improve the practical application of esculin, through the obtention of esculin mono and diacetates by fast and efficient biocatalysis reaction.