Microwave irradiation followed by zinc oxide based dispersive solid-phase extraction coupled with HPLC for simultaneous extraction and determination of flavonoids in Veronicastrum latifolium (Hemsl.) Yamazaki.

In this study, a sample preparation method involving microwave irradiation followed by dispersive solid-phase extraction was used to extract and separate flavonoids from Veronicastrum latifolium (Hemsl.) Yamazaki. Ethyl lactate was selected as the extraction solvent during microwave irradiation. Zinc oxide and ethanol were used as the adsorbents and the eluent, respectively, in dispersive solid-phase extraction. Several experimental parameters affected the extraction performance, such as the extraction solvent and method, the microwave irradiation time, temperature, and solid-to-liquid ratio, the type of adsorbent, the amount of sample solution, the adsorption time and method, and the type and volume of the eluent, and were investigated by single-factor and Box-Behnken design experiments in the pretreatment process. The recommended method was applied to extract flavonoids in Veronicastrum latifolium (Hemsl.) Yamazaki. The enriched flavonoids were analyzed for the first time by high-performance liquid chromatography, and seven flavonoids-vitexin, luteolin, wogonoside, apigenin, chrysoeriol, acacetin, and pectolinarigenin-were identified. Additionally, the method exhibited good linearity (r2 ≥ 0.9992) for flavonoids under the optimum conditions. Moreover, the relative standard deviation of the intraday and interday precision was less than 3.97%. The mean recoveries for flavonoids were more than 98.10%. This work is the first to report a method to extract, separate, and analyze flavonoids from Veronicastrum latifolium (Hemsl.) Yamazaki. Graphical Abstract Microwave irradiation followed by ZnO-based dispersive solid-phase extraction for the pretreatment of Veronicastrum latifolium (Hemsl.) Yamazaki samples, and high-performance liquid chromatography (HPLC) for analysis of enriched flavonoids.