Quality evaluation of Eucommiae Folium extracts and discovery of efficacy-associated quality markers based on spectrum-effect relationship

ABSTRACTThe spectrum-effect relationship between chemical fingerprints and antioxidant activities was established to evaluate the quality of Eucommiae Folium (EF) extracts and discover potential efficacy-associated quality markers. Characteristic fingerprints of different batches of EF extracts were generated by high-performance liquid chromatography (HPLC), and a similarity analysis was performed by hierarchical cluster analysis (HCA). Then the total antioxidant capacity assay kit with ferric reducing antioxidant assay (FRAP) method was used to determine antioxidant activity. The spectrum-effect relationship was established to identify the chemical constituents that impart antioxidant activities of Eucommiae Folium (EF) extracts using partial least squares regression (PLSR). HPLC fingerprints of EF extracts were established with the optimized chromatographic conditions: the mobile phase consisted 0.1% phosphoric acid -water (A) and acetonitrile (B), the detection wavelength was 326 nm, the column temperature was 30°C, and the flow rate was 0.8 mL/min. The correlation coefficient of similarity between 12 batches of extracts was ≥0.995. Compounds corresponding peaks P1, P2, P6 (chlorogenic acid), and P8 were closely related to the stable antioxidant activities of EF extracts, and could be selected as potential quality markers. An agile and efficient method that can ensure the intra-assay stability of biological activity of EF extracts and discover efficacy-associated quality markers was successfully built based on spectrum-effect relationship.