In this study, ultrasound-assisted alkaline hydrolysis was used to extract polyphenols from pitahaya peel. The effects of sonication time, ultrasonic density, NaOH concentration and the liquid–material ratio on the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of the extracts were studied. The composition and content difference of the extracts were analyzed and the inhibitory effect of α-amylase and α-glucosidase was measured. The results of single-factor analysis showed that when the sonication time was 45 min, the ultrasonic density was 32 W/L, the NaOH solution concentration was 6 M and the liquid–material ratio was 30 mL/g, the release of phenolic compounds was the largest and the antioxidant activity was the strongest. An UPLC-QTOF-MS/MS method was used to analyze the components and contents of the extracts. We found that there was a great difference in the component content of the free polyphenol extract and the bound polyphenol extract. From the results, we concluded that there was a strong correlation between the type and content of phenolic compounds and antioxidant activities, indicating that phenolic compounds were the main compounds of these biological activities. Moreover, the bound polyphenol extracts showed a significant inhibitory effect on α-amylase and α-glucosidase was stronger than that of the free polyphenol extracts. In addition, scanning electron microscopy showed that ultrasound-assisted extraction is crucial to the destruction of the cell wall and the release of bound polyphenols. Therefore, the pitahaya peel has the potential for therapeutic, nutritional, and functional food applications, and ultrasound-assisted alkaline hydrolysis is an effective means to release phenolic compounds.

本研究采用超声辅助碱解法从火龙果果皮中提取多酚。研究了超声处理时间、超声密度、NaOH浓度和液料比对提取物总酚含量（TPC）、总黄酮含量（TFC）和抗氧化活性的影响。分析了提取物的组成和含量差异，测定了α-淀粉酶和α-葡萄糖苷酶的抑制作用。单因素分析结果表明，超声处理时间为45 min、超声密度为32 W/L、NaOH溶液浓度为6 M、液料比为30 mL/g时，酚类化合物的释放量最大，抗氧化活性最强。采用 UPLC-QTOF-MS/MS 方法分析提取物的成分和含量。我们发现游离多酚提取物和结合多酚提取物的成分含量差异很大。从结果中，我们得出结论，酚类化合物的类型和含量与抗氧化活性之间存在很强的相关性，表明酚类化合物是这些生物活性的主要化合物。此外，结合多酚提取物对α-淀粉酶和α-葡萄糖苷酶的抑制作用明显强于游离多酚提取物。此外，扫描电子显微镜显示，超声波辅助提取对于细胞壁的破坏和结合多酚的释放至关重要。所以，