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

https://doi.org/10.1016/j.indcrop.2021.114140Get rights and content

Highlights

  • The synthesized solvent can successfully and efficiently converted polydatin to resveratrol.

  • The optimum extraction conditions of resveratrol were determined by response surface model.

  • The extraction process of resveratrol by NADES was analyzed by kinetic model.

  • The synthesized NADES was provided with the advantage of recycling.

Abstract

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.

Introduction

Resveratrol, a stilbenoid polyphenol, possesses two phenol rings bound by an ethylene bridge to each other (Mirhadi et al., 2021). Resveratrol exhibited various health benefits, including antioxidant, anti-viral, anti-inflammatory, anti-diabetes and antitumor activities (Ahmad and Hoda, 2020; Peng et al., 2013; Zhang et al., 2020). Natural plants, including grapes, peanut, blueberries, cranberries and some medicinal herbs such as P. cuspidatum and Veratrum grandiflorum, are the main sources of resveratrol (Fan et al., 2021; Sun et al., 2021). It is worth noting that the resveratrol in P. cuspidatum mainly exists in the form of glycosides, and its content is more than ten times higher than resveratrol (Chong et al., 2012). Therefore, it is a good approach to increase the content of resveratrol by transforming polydatin.

Normally, resveratrol is extracted by refluxing with 95 % ethanol from P. cuspidatum followed by liquid-liquid extraction using some organic solvents (Mantegna et al., 2012; Sun et al., 2021). This extraction process of resveratrol was complicated, time-consuming and involved a substantial amount of solvent. Recent studies have shown that acid hydrolysis or alkali hydrolysis can be used to improve the resveratrol yield in P. cuspidatum (Lin et al., 2016). This method can quickly and efficiently improve the yield of resveratrol, and possesses good benefits for industrial production. Subsequently, some researchers transformed and extracted resveratrol by enzymatic hydrolysis (Wang et al., 2013). Enzyme assisted extraction has the characteristics of green and environmental protection, and this approach addressed a problem was that related to solvent use and pollution. Chen et al. (2016) successfully transformed and extracted resveratrol with the assistance of glucose oxidase, but there are some disadvantages, such as, it takes too long, which was extremely unfavorable to industrial production. Therefore, it is still difficulty to establish an environmental, low-cost, convenient extraction and transformation process to acquire productive resveratrol from P. cuspidatum.

A new kind of solvent which deep eutectic solvent (DES) has lately been put forward as an environmentally friendly alternative to organic solvents, a combination of eutectic components (Abbott et al., 2001). Natural deep eutectic solvents (NADESs), as a subclass of DESs, are usually consisted of amino acids, polyhydric alcohols and some organic acids (Ali Redha, 2021). It is bio-degradable, reusable and miscible with water (Ali et al., 2020). Some studies have shown that DESs are effective in the extraction of natural products. Fan et al. (2020) effectively extracted harmine by menthol/anise alcohol-based NADES. Wang et al. (2020) introduced a sequence of DES systems to extract glycosides from Syringa pubescens Turcz. Chen et al. (2018) also obtained resveratrol by DESs from peanut roots. However, the above studies did not consider whether DESs has the function of transformation. Sun et al. (2021) successfully transformed and extracted resveratrol from P. cuspidatum with DESs, but in all the experimental system, the author added hydrochloric acid, so it was difficult to explain whether the conversion of polydatin was due to the presence of DESs or acid hydrolysis. The addition of hydrochloric acid was not green to the production and application of resveratrol. Moreover, the recycle of solvent and the recovery of resveratrol were not studied in depth.

To investigate whether DESs alone can be used for concurrent collection and conversion of polydatin into resveratrol from P. cuspidatum. In current research, choline chloride was selected as a hydrogen acceptor, different alcohols and some organic acids as hydrogen donors were used to synthesize NADES. The complete extraction process was shown in Fig. 1. The transformation and extraction parameters were systematically studied. Moreover, the reusability of NADES was investigated under the optimum extraction conditions. Meanwhile, the kinetic model Fick's second law and thermodynamics parameters were applied to investigate the mass transfer mechanism of resveratrol during the process of extraction. Finally, the oxidation activity of resveratrol was verified furthermore. Herein, a viable and sustainable transformation process was established for the development of the resveratrol from P. cuspidatum.

Section snippets

Materials and reagents

The obtained P. cuspidatum roots were dried from Beijing Tongrentang (Beijing, China) and broken up with a grinder and crossed by a 120-mesh sieve. Collected and stored the powder for the next experiment. In this experiment, choline chloride (> 98 %), acetic acid (≥99.5 %), glycerol (≥99 %), lactic acid (≥99 %), 1,3-butanediol (≥98 %) and 1,4-butanediol (≥98 %) were purchased from Aladdin Chemistry Co., Ltd. (Shanghai, China). Oxalic acid (≥99 %) and citric acid (≥99.5 %) were attained from

Screening suitable NADES solvent for converting and extracting resveratrol

The extraction efficiency of resveratrol was different due to the diversity of chemical properties about NADESs. The reason was that the acidity of NADES could affect the breaking of glycosidic bond in polydatin, which resulted in the increase of conversion efficiency and the yield of resveratrol (Oancea et al., 2012; Wan Mahmood et al., 2019). Here, we successfully prepared nine types of DES and measured their pH value. As can be seen from Fig. 2, the various forms of DESs had different

Conclusions

In conclusion, NADES (Choline chloride/Oxalic acid) can be used for simultaneous transformation and extraction of resveratrol in P. cuspidatum root. In the best conditions, liquid solid to liquid ratio 50 mg/mL, extraction temperature 75 ℃, extraction time 80 min, ultrasonic power 250 W, the output of resveratrol reached 12.31 mg/g and 96.11 % conversion efficiency was obtained. With the rise in temperature the mass transfer coefficient of resveratrol steadily increased and the final trend was

CRediT authorship contribution statement

All authors contributed to this article as follows:

Jian-Dong Wang: Experimental design, data processing and article writing. Li-Na Fu: Completed the extensive experiments in this paper. Li-Tao Wang: participated in the revision of the manuscript. Zi-Hui Cai and Yan-Qiu Wang: biological activity assessment. Qing Yang and Yu-Jie Fu: overall research guidance.

All authors have approved the final version to be published in Industrial Crops and Products.

All authors are responsible for the

Declaration of Competing Interest

The writers claim that the study reported in this paper does not have any established overlapping interests or personal relationships.

Acknowledgements

The authors gratefully acknowledge Fundamental Research Funds for Key Laboratory of Forest Plant Ecology, Ministry of Education Northeast Forestry University (K2020A01), the Central Universities (2572020DR07 and 2572019EA01), Research and development project of Applied Technology in Heilongjiang Province (GX18B003), the 111 Project (B20088) and Heilongjiang Touyan Innovation Team Program (Tree Genetics and Breeding Innovation Team).

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