Green extraction of polyphenol compound from walnut green husk by microwave-assisted choline chloride-based deep eutectic solvents: identification, kinetic, comparison and bioactivity

Yiwei Zhu; Weize Ma; Tongyuan Zhang; Chi Zhang; Aidong Sun

doi:10.1016/j.foodchem.2025.145438

Green extraction of polyphenol compound from walnut green husk by microwave-assisted choline chloride-based deep eutectic solvents: identification, kinetic, comparison and bioactivity

Food Chem. 2025 Jul 5;492(Pt 2):145438. doi: 10.1016/j.foodchem.2025.145438. Online ahead of print.

Authors

Yiwei Zhu¹, Weize Ma¹, Tongyuan Zhang¹, Chi Zhang¹, Aidong Sun²

Affiliations

¹ College of Biological Science and Technology, Beijing Key Laboratory of Forest Food Processing and Safety, Beijing Forestry University, Beijing 100083, China; Hebei Province Key Laboratory of Sustainable Utilization and Development of Forest Food Resources, Beijing Forestry University, Beijing 100083, China.
² College of Biological Science and Technology, Beijing Key Laboratory of Forest Food Processing and Safety, Beijing Forestry University, Beijing 100083, China; Hebei Province Key Laboratory of Sustainable Utilization and Development of Forest Food Resources, Beijing Forestry University, Beijing 100083, China. Electronic address: adsun@bjfu.edu.cn.

PMID: 40651140
DOI: 10.1016/j.foodchem.2025.145438

Abstract

Walnut green husks (WGH) emerged as promising substrates for the recovery of natural phenolic compounds and deserve consideration for waste recycling. In this study, a deep eutectic solvent (DES), choline chloride-fructose, was identified as the most suitable solvent for the preparation of polyphenols from WGH under a microwave-assisted system. With the parameters optimized by response surface methodology, the total phenolic content (TPC) of WGH extract reached 85 ± 3.02 mg GAE/g DW. The polyphenol identification results showed that isoquercetin was the major individual polyphenol in the WGH extract. The comparative experimental results with other methods indicated that microwave-assisted DES extraction (MAE-DES) enhanced the disruption of WGH, which caused the extract to exhibit higher TPC and antioxidant activity. Besides, DES provided better stability of phenolic compounds during the storage period. This study demonstrates that MAE-DES is a potential extraction technique for the recovery of highly bioactive phenolic compounds from food by-products.

Keywords: Antioxidant activity; Deep eutectic solvent; Kinetic; Microwave-assisted; Walnut green husk polyphenol.