Determination of Procyanidins in Extracts of Chinese Hawthorn Fruits by Quantitative 1H-NMR
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Abstract:
An analytical method to determine the content and the mean degree of polymerization (mDP) of the procyanidins in Chinese hawthorn extract was developed using quantitative nuclear magnetic resonance spectrometry (qNMR). 1H-NMR spectra were recorded using DMSO-d6 (dimethyl sulfoxide-d6) as the solvent and potassium biphthalate as the internal standard. According to the weight of the internal standard WR, the weight of sample WD, the absorption peak area AR（δ 7.529）of H-4 and H-5 from the internal standard, the absorption peak area A6,8（δ 5.787，5.702）of H-6 and H-8 from procyanidins, and the peak area Ae（δ 2.362）of H-4e at the end of the epicatechin unit, the mDP and content of the procyanidins in hawthorn extracts prepared from different batches were calculated based on the equations N = A6,8/Ae - 1 and C = (144 N + 1) A6,8 WR/51 (N + 1) ARWD ×100%, respectively. The results showed that there was a good linearity (r = 0.9996) within the range of 0.4~24 mg/mL and the average recovery was 104.6%. This method was applied to determine the content and mDP of procyanidins in hawthorn extract samples from two batches. The contents were 42.1% and 44.2% respectively; and the mDP values were 3.0 and 3.4, respectively.
