Fractionating the Flavonoids in Lonicerae japonicae Flos and Lonicerae flos via Solvent Extraction Coupled with Automated Solid-Phase Extraction

Due to the structural diversity of flavonoids in functional plant foods and the inherent limitations of existing techniques, it is important to develop a simple and green (environmentally friendly) method of extracting flavonoids from plant foods. In this study, a method involving solvent extraction followed by automated solid-phase extraction was developed for extracting flavonoids from Lonicerae japonicae flos (JYH) and Lonicerae flos (SYH), both of which are widely used functional plant-based foods in Asian countries. For the optimisation of the solvent extraction method, solvent concentration (0.0, 20.0, 40.0, 60.0, 80.0 and 100.0% (v/v) of ethanol–water solution), extraction temperature (40, 60 and 80 °C) and extraction time (15.0, 30.0, 60.0, 90.0 and 120.0 min) were evaluated via design of experiment after screening. For solid-phase extraction, five cartridges (Strata-X, InertSep RP-2, InertSep RP-C18, Bond Elut-ENV, Oasis Prime HLB) were evaluated and different elution steps were optimised to obtain high recoveries (79.69–140.67%) for eight target flavonoids, including rutin, isoquercetin and luteolin. Antioxidant capacity assays revealed that JYH samples demonstrated superior antioxidant potential compared to SYH. The optimised extraction method provides a valuable tool for industrial-scale flavonoid production.