Phytosteryl sinapates and vanillates: chemoenzymatic synthesis and antioxidant capacity assessment

Phytosterols and their derivatives have attracted much attention because of their health benefits to humans and are widely used in food, pharmaceuticals, and cosmetics in the past decades. While most of the research has focused on free phytosterols and phytosteryl esters of fatty acids, few researches reported on phytosteryl phenolates, the esters of phytosterols with phenolic acids. Two novel group phytosteryl phenolates, namely phytosteryl sinapates and vanillates, were successfully chemoenzymatically synthesised in this work and their structures confirmed. Fourier transform infrared (FTIR) and high performance chromatography-mass spectrometry/mass spectrometry (HPLC-MS/MS) using atmospheric pressure chemical ionisation (APCI) under both positive and negative ion modes were employed for this purpose. High antioxidant capacity of phytosteryl sinapates was observed using both oxygen radical absorbance capacity (ORAC) assay and cooked ground meat model system. Although phytosteryl vanillates showed lower antioxidant capacity than phytosteryl sinapates, they were stronger antioxidants than vanillic acid and vinyl vanillate in both assays employed. Conjugation of phytosterols with sinapic or vanillic acid rendered higher antioxidant capacity. Further studies on health benefits of phytosteryl sinapates and vanillates are necessary.