Determination optimization of polyphenols content in pomegranate- peel extracts by Folin-Ciocalteu colorimetry | Folin-Ciocalteu比色法测定石榴皮多酚含量条件的优化

Chinese. 系统研究Folin-Ciocalteu (FC)比色法测定石榴皮中多酚含量的最佳反应条件，为进一步开发利用石榴皮资源提供有效的测试手段。以没食子酸为标准物质，考察FC试剂浓度、Na2CO3质量浓度、反应时间和反应温度4个因素对FC比色法测定石榴皮多酚含量的影响，用L9(34)正交试验对测定条件进行优选，并对FC比色法的测定效果进行评定。适宜的显色条件是：FC试剂浓度为0.6 mol/L，Na2CO3质量浓度为0.150 g/mL，在25 ℃避光条件下反应50 min后，于765 nm处测吸光值。1～6 mg/L没食子酸的吸光度值与其质量浓度呈良好的线性关系，相关系数R2＝0.995 8。在优化条件下测得石榴皮中多酚含量为287.46 mg/g,平均回收率为99.31%,平均相对标准偏差(RSD)为1.98%。FC比色法具有试剂用量少、检测速度快、准确度高、精密度高、稳定性好等优点，可用于石榴皮中多酚含量的测定。

English. The study was to investigate an optimal colorimetric method to determine polyphenols in pomegranate peel systematically, and to provide an effective way to estimate the polyphenols for the value of pomegranate-peel. Using gallic acid as standard to select the density of Folin-Ciocalteu, sodium carbonate solution, reaction time and reaction temperature as impacting factors, the orthogonal design test L9(34) was used to study-optimized measurement conditions, and the method was evaluated at last. The optimum colorimetric conditions were determined as follows: the concentration of Folin-Ciocalteu reagent and Na2CO3 were 0.6 mol/L and 0.150 g/mL, reaction 50 minutes in temperature 25 ℃ away from light. There was a good linearity between the absorbance and gallic acid concentration from 1-6 mg/L (R2＝0.995 8) in 765 nm. The pomegranate peel polyphenols can obtain a yield of 287.46 mg/g in this method. The average spiked recovery was 99.31%, with a RSD of 1.98%. This method, with a little reagent, fast, accurate, sensitive and stable, can be used as an appropriate method to measure the polyphenols in pomegranate-peel extracts.