# Valorization of Quince By-Products Using Natural Deep Eutectic Solvents (NADES): Extraction and In Vitro Digestion of Phenolic Compounds

## TL;DR

This study explores using natural deep eutectic solvents to extract valuable phenolic compounds from quince by-products, showing they are more effective than ethanol and could help create health-promoting food products.

## Contribution

The study introduces NADES as a superior alternative to ethanol for extracting and improving the digestibility of phenolics from quince by-products.

## Key findings

- Organic acid-based NADES like ChCl:MA and ChCl:LA extracted significantly more phenolics from quince peel than ethanol.
- Glucose- and glycerol-based NADES increased bioaccessibility of phenolics in quince core beyond 100%.
- NADES improved antioxidant capacity retention after simulated digestion compared to ethanol.

## Abstract

Quince (Cydonia oblonga Mill.) processing generates peel and core by-product fractions that are underexploited resources with untapped potential for valorization in sustainable food systems. In this study, ultrasound-assisted extraction was performed using several choline chloride-based natural deep eutectic solvents (NADES, six formulations with distinct hydrogen-bond donors) and compared with 70% (v/v) ethanol. Extracts were analyzed for total phenolic content, antioxidant capacity, and individual phenolic compounds by LC-MS/MS, and their bioaccessibility was determined through a standardized in vitro digestion model. Organic acid-based NADES, particularly ChCl:MA (2:1) and ChCl:LA (1:1), yielded significantly higher phenolic contents from the peel than ethanol (up to ~45% increase, p < 0.05), and ChCl:MA maintained superior antioxidant capacity after digestion. In the core fraction, glucose- and glycerol-based NADES promoted the release of bound phenolics, resulting in bioaccessibility values exceeding 100%, indicating the release of previously bound phenolics under digestive conditions. The present study provides novel insights into the effects of NADES on both extraction efficiency and digestibility of quince by-products. These findings highlight quince peel and core as promising raw materials for developing functional food and nutraceutical ingredients, thereby offering a feasible strategy for upcycling fruit-processing residues into health-promoting applications.