Determination of flavonoids in the flowers of <Emphasis Type="Italic">Paulownia tomentosa</Emphasis> by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) technique coupled with photodiode array (PDA) detection was developed for the simultaneous determination of four flavonoids, i.e. apigenin (AP), diplacone (DI), mimulone (MI) and 5,4′-dihydroxy-7,3′-dimethoxyflavanone (DDF) in extracts of the flowers of Paulownia tomentosa. The optimized method was proposed for the separation and detection of the selected constituents, using methanol-1% acetic acid as the mobile phase at a flow rate of 0.8 mL/min, 290 and 267 nm as the detection wavelengths. All the flavonoids showed good linearity in a relatively wide concentration range (r > 0.9999). The detection limits for the analytes ranged from 0.2 to 4.0 ng, at a signal-to-noise ratio of 3. Inter- and intra-assay accuracy and precision were all lower than 5.0%. The recovery of the method was 95.9–101.9%. Moreover, the optimized HPLC method was employed to analyze the flowers of Paulownia tomentosa.