Lipophilization of phenolic acids with phytosterols by a chemoenzymatic method to improve their antioxidant activities

Abstract

In this study, a two‐step method for chemoenzymatic lipophilization of phenolic acids with phytosterols was studied. Optimal conditions for esterification involved the use of a binary solvent containing hexane and 2‐butanone (3 mL, 8:2, v/v), a relatively equal molar ratio of vinyl ester to phytosterols (0.1 mmol), and 100 U/mL of lipase from Candida rugosa at 55°C. Various phenolic acids were used, but only ten of them were successes. Their antioxidant activities were evaluated by total oxidation (TOTOX) value and thiobarbituric acid reactive substances (TBARS) value. Phytosteryl 4‐hydroxybenzoate, phytosteryl vanillate, and phytosteryl ferulate showed potential for use as food antioxidants.Practical applications: There is increasing interest in the development of antioxidants from natural sources because of the concerns about the safety of synthetic antioxidants. Lipophilization of phenolic acids was carried out to improve the hydrophobicity and change the antioxidant capacity of phenols. This study focuses on phytosterol, which is a food‐grade mixture of steroid compounds, having development and application potential as a cost effective food additive. According to our results, phytosteryl phenolates, which are defined as esters between phytosterols and phenolic acids, have the potential for use as alternative food antioxidants in the food industry.The lipophilization of phenolic acids with phytosterols was carried out via a two‐step chemoenzymatic route as the figure showed. The intermediate vinyl esters were first chemically produced and subsequently esterified with phytosterols catalyzed by lipase from Candida rugosa.