Enzymatic synthesis of a catecholic polyphenol product with excellent antioxidant activity

Polyphenols, especially catecholic stilbene derivatives, have attracted much attention due to the huge pharmacological effects and promising health benefits. However, their chemical synthesis via regioselective ortho-hydroxylation on aromatic rings is highly challenging. In this study, 3′-hydroxypterostilbene (HPS) is taken as a model product due to its strong potential as an antitumor agent. One-step enzymatic synthesis of HPS from pterostilbene (PS) was explored, with immobilised tyrosinase as catalyst. The impact of solvent, pH, temperature, oxygen and reductant concentration on the reaction was investigated, and the conversion was optimised by employing the response surface methodology (RSM). Finally, a high yield of 77.9% was obtained in 2.7 h. This study demonstrates the first successful use of a biotechnological strategy to synthesise HPS. The antioxidant activities of both PS and HPS were evaluated by using the DPPH assay, demonstrating that HPS is more potent than PS as a radical scavenger.