Optimization of Isoliquiritigenin Extraction From Liquorice and Assessment of Antioxidant Activity Using an Ionic Liquid‐ Aspergillus niger Fermentation System

Abstract

ABSTRACT This study aimed to develop an environmentally benign and efficient extraction process for isoliquiritigenin (ILS) from Glycyrrhiza uralensis Fisch. Previously, the application of ionic liquid (IL)‐assisted extraction technology for the specific separation and extraction‐bioconversion coupling of rare bioactive constituents, including synergistic solid‐state fermentation (SSF) with Aspergillus niger (AN), remained largely unexplored. Herein, a composite extraction system was established by integrating IL with AN‐SSF. Response surface methodology (RSM) was employed to optimise the process under the following conditions: solid‐to‐liquid ratio of 1:4 (g/mL), pH 3, AN concentration of 5 × 10 5 CFU/mL, fermentation period of 4 days, fermentation carbon content of 5%, fermentation nitrogen content of 5%, and 0.3 mol/L 1‐butyl‐3‐methylimidazolium acetate as the IL. The optimised process yielded an ILS of 0.0347 mg/g, representing a 1.7‐fold significant enhancement in extraction efficiency compared to conventional ethanol ultrasonic extraction. Furthermore, the antioxidant capacity of ILS was evaluated via in vitro antioxidant assays, including 1,1‐diphenyl‐2‐picrylhydrazyl radical (DPPH·) and hydroxyl radical (·OH) scavenging experiments, combined with network pharmacology analysis. Results demonstrated that ILS exerted significant free radical scavenging activity (·OH scavenging rate: 75.13 ± 0.006%; DPPH· scavenging rate: 56.57 ± 0.77%) with a dose‐response relationship. Mechanistically, network pharmacology predicts that ILS may target core receptors (e.g., IGF1R ) and synergistically regulate the PI3K/AKT‐FoxO and Nrf2‐ARE signalling pathways. This putative mechanism involves upregulating antioxidant enzymes ( SOD1, CAT, HO‐1 ) and suppressing ROS generation, which awaits validation via molecular and cellular experiments. In vitro antioxidant assays confirmed that ILS exerts marked dose‐dependent free radical scavenging activity (·OH: 75.13 ± 0.006%; DPPH·: 56.57 ± 0.77%). Collectively, this study uncovers the “single‐component‐multiple‐targets‐multiple‐pathways” antioxidant mechanism of ILS, providing a theoretical foundation for its subsequent development and application.