Purification, Ionic-Liquid-Associated Elemental Marker Reduction, Stability and Bioactivity Evaluation of Monoterpene Glycoside-Enriched Extracts from Radix Paeoniae Alba

Ionic liquid-assisted extraction can improve the recovery of monoterpene glycosides from Radix Paeoniae Alba, whereas post-extraction purification and ionic-liquid-associated marker-level quality control remain necessary before further bioactivity evaluation. In this study, a macroporous resin-based purification process was developed for monoterpene glycoside-enriched extracts obtained by conventional reflux extraction and ionic liquid-assisted microwave–ultrasound extraction. Among the five tested resins, AB-8 resin showed the best adsorption performance and was selected for further process optimization. The optimized purification conditions were a loading concentration of 13 mg/mL, loading pH of 7, elution with 70% ethanol, loading volume of 6 BV and elution volume of 9 BV. After purification, the total quantified monoterpene glycoside content increased from 6.59% to 51.68% in the conventional extract and from 15.30% to 75.30% in the ionic liquid-assisted extract. The ionic-liquid-associated elemental marker content in the ionic liquid-assisted extract decreased from 5.593% to 0.072% after purification, corresponding to an approximately 98.7% reduction at the elemental-marker level. Stability evaluation indicated that Na2SO3, Fe3+, ascorbic acid, sucrose and light exposure affected the detected monoterpene glycoside content to different extents, whereas short-term heating within 20–80 °C caused only slight fluctuations. The purified extracts showed stronger DPPH and ABTS radical scavenging activities and reducing power than the crude extracts. In LPS-stimulated RAW264.7 cells, the purified extracts reduced NO production and downregulated the mRNA expression of IL-6, IL-1β, TNF-α, iNOS and COX-2, suggesting anti-inflammatory potential at the NO and gene-expression levels. AB-8 resin purification enriched the monitored monoterpene glycosides, reduced the selected ionic-liquid-associated elemental marker, and generated purified fractions suitable for subsequent stability and bioactivity evaluation.