Platycodon grandiflorum roots (PGR) is a medicinal plant rich in triterpenoid saponins, which are known for their antioxidant properties. In this study, ultrasonic-assisted extraction (UAE) was employed to extract total saponins from PGR, with the extraction process optimized through single-factor experiments and response surface methodology (RSM). The optimal extraction conditions were determined to be an extraction time of 51.04 min, ultrasonic power of 153.79 W, and a temperature of 49.59°C, resulting in a saponins yield of 4.83 %. Purified using n-butanol extraction followed by ethanol elution produced four distinct fractions, with the PAE-3 fraction containing the highest saponins concentration, primarily composed of Platycodin G1 and Platycodin E. In vitro antioxidant assays revealed that PAE-3 exhibited the strongest radical scavenging capacity and reducing power. A strong negative correlation between the content of Platycodin G1 and Platycodin E and IC₅₀ values in antioxidant assays suggests that these compounds are key contributors to the antioxidant activity of PAE-3. In vivo studies using Caenorhabditis elegans further validated the antioxidant potential of PAE-3, showing a significant reduction in reactive oxygen species levels and enhanced activity of superoxide dismutase (SOD) and glutathione (GSH). UPLC-Q-TOF/MS analysis identified the structure of Platycodin G1 and Platycodin E, while molecular docking revealed strong binding affinities of these compounds to SOD and GSH-Px, emphasizing their roles in antioxidant defense. Overall, this study highlights the efficacy of UAE in optimizing the saponins yield and underscores the potent antioxidant properties of enriched saponins fractions, offering promising application potential for the development of natural antioxidants.

中文翻译：

---

超声辅助提取和大花桔梗根中三萜皂苷的抗氧化活性：优化、纯化和分子见解


桔梗大花根 （PGR） 是一种富含三萜皂苷的药用植物，三萜皂苷以其抗氧化特性而闻名。在本研究中，采用超声波辅助提取 （UAE） 从 PGR 中提取总皂苷，并通过单因素实验和响应面法 （RSM） 优化提取过程。确定最佳提取条件为提取时间为 51.04 min，超声功率为 153.79 W，温度为 49.59°C，皂苷收率为 4.83 %。使用正丁醇提取纯化，然后乙醇洗脱产生四个不同的馏分，其中 PAE-3 馏分含有最高的皂苷浓度，主要由 Platycodin G1 和 Platycodin E 组成。体外抗氧化测定表明，PAE-3 表现出最强的自由基清除能力和还原能力。抗氧化测定中桔梗素 G1 和桔梗素 E 的含量与 IC₅₀ 值之间存在很强的负相关关系，表明这些化合物是 PAE-3 抗氧化活性的关键贡献者。使用秀丽隐杆线虫的体内研究进一步验证了 PAE-3 的抗氧化潜力，显示活性氧水平显着降低，超氧化物歧化酶 （SOD） 和谷胱甘肽 （GSH） 活性增强。UPLC-Q-TOF/MS 分析鉴定了桔梗素 G1 和桔梗素 E 的结构，而分子对接揭示了这些化合物与 SOD 和 GSH-Px 的强结合亲和力，强调了它们在抗氧化防御中的作用。 总体而言，本研究强调了 UAE 在优化皂苷产量方面的功效，并强调了富集皂苷组分的强大抗氧化特性，为天然抗氧化剂的开发提供了有前途的应用潜力。