Synthesis of Resveratrol-Butyrate Esters

The mixtures of RBEs were synthesized based on our protocol, as described previously [13 (link)]. The butyric acid (ACROS, Morris Plains, NJ, USA) was mixed with resveratrol (TCI Development Co., Ltd., Shanghai, China) in tetrahydrofuran (Echo Chemical Co., Ltd., Miaoli County, Taiwan). Later, N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide (Sigma-Aldrich, Saint Louis, MO, USA) and 4-dimethylaminopyridine (Sigma-Aldrich, Saint Louis, MO, USA) were added. Then, the esterification reaction was conducted by avoiding light for 48 h. Upon completion, the reaction mixture was mixed with distilled water and filtered in order to obtain the precipitated RBEs. The RBEs were kept within a −20 °C freezer.