Adaptability Study of the Complexation and Color Rendering Systems on Determination of Total Flavonoids in Kunlun Coreopsis tinctoria by Spectrophotometry

This work aimed at choosing of a suitable spectrophotometric method for the analysis of Coreopsis tinctoria flavonoids (CTFs). Firstly, the total flavonoids in Coreopsis tinctoria were extracted with 60% ethanol (v/v). Then petroleum ether, ethyl acetate and n-butanol were used successively to soke the total flavonoids and the petroleum ether extract, ethyl acetate extract (EAE) and n-BuOH-E extract (n-BuOH-E) were obtained separately. The content of flavonoids in EAE and n-BuOH-E were detected by classical complexation and color rendering systems including NaNO₂-Al (NO₃) ₃/AlCl₃-NaOH and KAc-Al (NO₃) ₃/AlCl₃, and rutin, quercetin and epicatechin (EC) were used as reference substances, respectively. The content of flavonoids in EAE and n-BuOH-E were also determined simultaneously by high performance liquid chromatography (HPLC) to verify the adaptability of the different complexation method. HPLC results showed that the content of flavonoid in EAE and n-BuOH-E was 48.43% and 43.19% respectively. By comparison, the content of flavonoids in EAE and n-BuOH-E measured with rutin KAc-AlCl₃ system was closest to that determined by HPLC. Therefore, rutin KAc-AlCl₃was considered to be the optimal method for the determination of CTFs. Then rutin KAc-AlCl₃method was used to the detection of total flavonoids in Coreopsis tinctoria and the result was 10.65%.