Simultaneous transformation and extraction of resveratrol from Polygonum cuspidatum using acidic natural deep eutectic solvent

Resveratrol, as a natural antioxidant, has been studied widely for its antioxidant, anti-inflammatory, anti-apoptotic, and anticancer properties. In this study, a strategy was developed to transform and extract resveratrol from Polygonum cuspidatum on the basis of NADES (natural deep eutectic solvent). In the series of adjustments and optimizations by single-factor experimental, the optimum NADES system (choline chloride to oxalic acid was 1:1) and other experimental conditions were determined, including water content of NADES, solid-liquid ratio, extraction time, extraction temperature and ultrasonic power. At the same time, RSM combined with BBD further optimized the experimental process, the results obtained by RSM optimization showed that the resveratrol yield of 12.31 mg/g was achieved when solid-liquid ratio was 1:50, temperature was 75℃ and time was 80 min. Meantime, the conversion efficiency of polydatin was 96.11 % and the content of resveratrol increased 6-fold higher than that of untreated sample. The kinetic of extraction and thermodynamic analysis were performed at different extraction temperatures to examine the temperature on the impact of the resveratrol extraction from P. cuspidatum. Ethyl acetate was used for back extraction in order to achieve the recycling of solvent and the recovery of resveratrol from NADES. The results showed that ethyl acetate had a good extraction effect and NADES still had a high capacity to convert and extract resveratrol after three cycles. In addition, the extracts exhibited superior antioxidant activity with higher content of recovered resveratrol. This established process can therefore be used to extract and recover resveratrol from plants as an environmental, pollution-free alternative approach.