The HPLC-PDA Method for Simultaneous Determination of Regalosides from Bulbs of Thunb. and Their Antioxidant Effects.

Thunb. is a herbal medicine that is widely used to treat inflammation and lung diseases. In this study, a simultaneous quantitative method was developed for the quality control of BLL using high-performance liquid chromatography coupled with a photodiode array detector (HPLC-PDA), and their antioxidant effects were evaluated. Eight regalosides (i.e., regaloside A, B, C, E, F, H, I, and K) were selected as marker substances and separated on a Gemini C reversed-phase analytical column by gradient elution with distilled water-acetonitrile mobile phase containing 0.1% () formic acid. The method was validated with respect to linearity, sensitivities (limit of detection (LOD) and limit of quantitation (LOQ)), accuracy, and precision. The antioxidant effects of the extract and each component were evaluated using the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay and 2-2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assay. The coefficients of determination values used as indicators of linearity for all components were ≥0.9999. LOD and LOQ concentrations were 0.10-0.66 μg/mL and 0.29-2.01 μg/mL, respectively. The recovery was 95.39-103.925% (relative standard deviation; RSD ≤ 2.55%), and precision RSD was <2.78%. The HPLC-PDA method was applied to real samples, and all components were detected at 1.12-29.76 mg/freeze-dried g. The evaluation of antioxidant effects showed that regalosides C, E, and K exhibited significant antioxidant effects. Our knowledge will be appropriately utilized in raw material management and conducting clinical and non-clinical studies on or herbal medicine prescriptions containing .