Abstract:

A HPLC method was proposed to analyze the variation of total flavonoids content during processing of Eucommia staminate flower tea. Samples were extracted using 50% methanol solution-concentrated sulfuric acid (20:1, V/V) and cleaned up using ethyl acetate. The HPLC analysis was performed on a Kromasil-C18 column (4.6 mm × 250 mm, 5 μm) with methanol- 0.4% phosphoric acid (60: 40, V/V) as the mobile phase at the flow rate of 1.0 ml/min, and the column temperature and the detection wavelength were set as 25℃ and 360 nm, respectively. The external standard method was applied to quantification using quercetin as the reference substance. There was a good linear relationship between HPLC peak area and quercetin concentration in the range of 0.05－0.55 g/L. The average recovery for quercetin in spiked Eucommia staminate flower tea was 98.82% with a RSD of 0.96%. The method is convenient, accurate and can be applied in the quantitative determination of total flavonoids in the processing of Eucommia staminate flower tea. The fixation resulted in the fall of content of total flavonoids, while the following primary and advanced frying led to the gradual rise. Through the procedures of fixing, primary frying and advanced frying, the content of total flavonoids in fresh Eucommia staminate flower was elevated by 25.88%.

Key words: Eucommia staminate flower tea, total flavonoids, HPLC