title: Chromatographic and electrochemical determination of quercetin and kaempferol in phytopharmaceuticals.
abstract: An NP-HPLC method both with diode-array (DAD) and electrochemical detection (ED) was developed and validated for the determination of quercetin and kaempferol, the principal active constituents in phytopharmaceuticals of Ginkgo Biloba. Calculated retention of the two flavonoids was contrasted with experimental values in five different reversed phase columns for methanol-water, acetonitrile-water, THF-water and dioxane-hexane binary mixtures as mobile phases. The capacity factor k, selectivity alpha and asymmetry factor F were evaluated and compared in DAD-RP-HPLC, DAD-NP-HPLC, ED-RP-HPLC and ED-NP-HPLC. The methods were used for the quantitative analysis of acid hydrolyzed extracts of tablet phytopharmaceuticals. Calibration curves were linear within the range 10 and 40 microg ml(-1) for the DAD and 10-270 microg ml(-1) for the ED, whereby limits of detection ranged from 0.5 microg ml(-1) (quercetin) to 0.1 microg ml(-1) (kaempferol). The electrochemical method based on differential pulse voltammetry (DPV) with a C-PVC electrode resolved the quercetin and kaempferol peaks and exhibited a two orders higher sensitivity in comparison with a carbon fiber electrode. DPV calibration curves were linear within the range 96-300 microg ml(-1) for quercetin and 68-960 microg ml(-1) for kaempferol. The respective oxidation peaks appeared at 462 and 518+/-2 mV and were used in the direct determination of quercetin in extracts of commercial phytopharmaceuticals.
authors.affiliation: Facultad de Ciencias Químicas, Universidad Autónoma de Puebla, Apartado Postal J-55, Puebla, Pue. 72571, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Aguilar-Sánchez
authors.forename: F
authors.initials: F
authors.lastname: Ahuatl-García
authors.forename: M M
authors.initials: MM
authors.lastname: Dávila-Jiménez
authors.forename: M P
authors.initials: MP
authors.lastname: Elizalde-González
authors.forename: M R G
authors.initials: MR
authors.lastname: Guevara-Villa
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004355:Drug Stability; D004563:Electrochemistry / Q000379:methods*; D020441:Ginkgo biloba / Q000737:chemistry; D044949:Kaempferols / Q000032:analysis*; D004364:Pharmaceutical Preparations / Q000032:analysis; D010936:Plant Extracts / Q000032:analysis* / Q000737:chemistry; D011794:Quercetin / Q000032:analysis*; D015203:Reproducibility of Results; D013607:Tablets
chemical_list: D044949:Kaempferols; D004364:Pharmaceutical Preparations; D010936:Plant Extracts; D013607:Tablets; C006552:kaempferol; D011794:Quercetin