Optimisation of Green Extraction and In Vitro Antioxidant Activities of Polyphenols from Aiweixin Oral Liquid Residues Using UPLC-MS-Based Targeted Metabolomics

This study aimed to characterise the polyphenolic profile and evaluate the extractability of Aiweixin Oral Liquid (AWX) residues, identify polyphenolic components via targeted metabolomics, optimise ultrasonic extraction, assess in-vitro antioxidant capacity, and explore extraction-synergy mechanisms by microstructural analysis to support high-value recycling of compound Chinese medicine residues. UPLC-Q Exactive MS was used to quantify 25 polyphenols. Single-factor tests combined with Box–Behnken response-surface methodology optimised ultrasonic-assisted deep-eutectic-solvent (DES) extraction of total polyphenols. Multiple in-vitro antioxidant assays and comparative morphological observation by light microscopy and SEM were carried out. Twenty-five polyphenols, mainly phenolic acids, were characterised in AWX residues, with gallic acid (361.57 μg/g) as the most abundant constituent. The optimal conditions were liquid-to-solid ratio of 62 mL/g, DES molar ratio 1:3, ultrasonic time 50 min, and power 445 W, yielding better extraction efficiency than ethanol or water. The extract exerted dose-dependent radical-scavenging effects against DPPH, ABTS, and PTIO alongside strong reducing power. Microscopy showed ultrasonic-DES treatment destroyed residues ducts, fibres, and cells, verifying ultrasonic cavitation-promoted constituent release. AWX residues are abundant in bioactive polyphenols. This eco-friendly, high-efficiency DES-ultrasonic approach yields antioxidant-rich extracts and provides a viable theoretical basis for the resource recovery and further development of waste materials from compound traditional Chinese medicines.