In this study, the conditions of extraction of loquat flowers polyphenolics were optimized through response surface methodology (RSM). Proper extraction conditions were: solid to liquid ratio 1 g per 50 mL and ethanol concentration 50% at 61°C for 9 min. Furthermore, the antioxidant and anti-polyphenol oxidase (PPO) activity of purified total polyphenolics (PTP) were investigated. PTP displayed strong antioxidant activity with IC50 values of 126.3 ± 8.9, 162.4 ± 6.3 and 94.97 mg ascorbic acid equivalent/g dry weight (mg AAE/d.w.) for ABTS, DPPH, and FRAP assays. In addition, PTP has a substantial inhibitory activity on PPO (IC50 = 115 ± 9.2 μg/mL). From the kinetics analysis, it was proved to be a reversible and mixed-type inhibitor of PPO with KI and KIS values of 76.77 μg/mL and 227.86 μg/mL, respectively. Further, the molecular mechanism underlying the inhibition of PPO by PTP was investigated by molecular docking techniques. The results showed that PTP units could form interaction with the catalytic pocket of PPO through the interaction with amino acid residues in the enzyme active center. The antioxidant activities of PTP together with its effect on PPO activity provide a strong starting point for their practical usage in the food industry.

中文翻译：

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枇杷花多酚提取工艺优化及其抗氧化和抗多酚氧化酶特性

本研究采用响应面法（RSM）对枇杷花多酚的提取条件进行优化。合适的提取条件为：固液比1 g/50 mL，乙醇浓度50%，61℃，9 min。此外，还研究了纯化的总多酚（PTP）的抗氧化和抗多酚氧化酶（PPO）活性。PTP 显示出很强的抗氧化活性，ABTS、DPPH 和 FRAP 测定中的 IC50 值为 126.3 ± 8.9、162.4 ± 6.3 和 94.97 mg 抗坏血酸当量/g 干重 (mg AAE/dw)。此外，PTP 对 PPO 具有显着的抑制活性 (IC50 = 115 ± 9.2 μg/mL)。动力学分析证明其是一种可逆的混合型PPO抑制剂，KI和KIS值分别为76.77 μg/mL和227.86 μg/mL。此外，通过分子对接技术研究了PTP抑制PPO的分子机制。结果表明，PTP单元可以通过与酶活性中心的氨基酸残基相互作用，与PPO的催化口袋形成相互作用。PTP 的抗氧化活性及其对 PPO 活性的影响为其在食品工业中的实际应用提供了强有力的起点。