Fluorescence enhancement of flavonoids and its application in ingredient determination for some traditional Chinese medicines by CE-LIF

Flavonoids are widely used in the treatment of various diseases due to their antioxidant, anti-inflammatory, anticancer and antiviral properties. Fluorescence detection is rarely applied for the determination of flavonoids because of their weak fluorescence. In this work, a method of fluorescence enhancement of flavonoids was firstly introduced by using sodium acetate for flavonoid derivatization. The study discovered that flavonoids, with a hydroxyl at the C3 position, had the ability to emit strong fluorescence after derivatization. Five flavonoids, kaempferide, galangin, isorhamnetin, kaempferol and quercetin, having a special structure, were selected, derivatized and analyzed by capillary electrophoresis with laser-induced fluorescence detection. Under the optimal conditions, the five flavonoids could be completely separated within 3 minutes. Good linear relationships were obtained for all analytes and the limits of detection for the five flavonoids were in the range of 1.18-4.67 x 10(-7) mol L-1. Finally, the method was applied to the determination of flavonoids in five traditional Chinese medicines: aster, chamomile, galangal, tangerine peel and cacumen biotae. Flavonoids were successfully found in all these medicines by the developed method. The recoveries were in the range of 84.2-111%. The method developed in this study was fast, sensitive and reliable for the determination of flavonoids.

Automated summary

Flavonoids are widely used in the treatment of various diseases due to their antioxidant, anti-inflammatory, anticancer and antiviral properties. In this study, a method of fluorescence enhancement of flavonoids was introduced for the first time using sodium acetate for flavonoid derivatization. Five specific flavonoids were successfully separated and analyzed by capillary electrophoresis with laser-induced fluorescence detection. The developed method was then applied to the determination of flavonoids in traditional Chinese medicines, and the presence of flavonoids was confirmed in all tested medicines. The method proved to be fast, sensitive and reliable for the determination of flavonoids.