Antioxidant activity of EGC (epigallocatechin) ester derivatives in food and biological model system

Abstract

Objective: Antioxidants retard oxidative processes in food and pharmaceuticals as well as in the body. However, potential adverse effects of synthetic antioxidants and insufficient efficacy of current natural/natural-derived antioxidant substitutes necessitate developing novel antioxidants. Thus, EGC, as one of the most widely distributed dietary flavanols, serves as an efficient natural antioxidant with numerous health effects, but it is relatively poorly soluble in lipophilic media. In this study, novel lipophilic EGC derivatives prepared via enzymatic esterification will be evaluated in controlling oxidation in food and biological systems.
Methods: EGC esters were prepared under optimized reaction conditions, including enzyme type, substrate ratio (Acyl acceptor/acyl donor), and reaction time. The purified products were then tested for their antioxidant ability using β-carotene bleaching, LDL (low-density lipoprotein) oxidation, and DNA scission assays.

Results: In the β-carotene bleaching assay, the oxidation inhibition of EGC and its esters was observed for about 80 min at 50℃ by maintain the yellow colour and then decreased gradually with time. Meanwhile, EGC monoesters (except EGC acetate and stearate) showed a significantly higher inhibition rate than EGC. In the LDL oxidation assay, a similar downtrend of antioxidant ability was observed. However, EGC exhibited higher antioxidant capacity compared to EGC monoesters. In the DNA scission test, the EGC acylated with short-chain fatty acids (C2-C6) showed the higher DNA stability than EGC or other EGC monoesters.

Conclusion: Overall, EGC monoesters displayed significant antioxidant activity in all three assays. The results in biological/food systems were in agreement with our previous chemical antioxidant tests. Moreover, the antioxidant ability of EGC as a natural antioxidant was retained or even enhanced after modification. Thus, acylated EGCs could serve as viable alternatives to traditional synthetic antioxidants.