Abstract In this study, stability including the total flavonoids content (TFC) and main monomers composition and antioxidant activity of the flavonoids extract (LBLF) from Lycium barbarum leaves were investigated in the process of simulated oral and gastrointestinal digestion in vitro. During digested through the simulated oral fluid (SOF), gastric fluid (SGF), and intestinal fluid (SIF) in order, TFC of LBLF in the lyophilized digestive fluid samples were determined at different time points. It was shown that compared with the initial TFC of 811.72 ± 0.72 mg RE/g DW, the total flavonoids did not change significantly during oral digestion, while definitely increased at gastric digestion stage (p < 0.05) where the pH value is the lowest in the digestive system, indicating that the release of flavonoids from LBLF was promoted by pepsin, trypsase, and bile, however decreased during intestinal digestion probably due to the instability of LBLF in weak alkali media. Moreover, the antioxidant capacity and bioaccessibility of LBLF were significantly improved by SGF and SIF digestion (p < 0.05). The scavenging effect of the fluid sample after gastric digestion on free radicals followed as O2 − · > ABTS+ · > DPPH > ·OH > FRAP, while the clearance effect of intestinal digestion sample expressed as ABTS+ · > O2 − · > DPPH > FRAP > ·OH. High performance liquid chromatography (HPLC) results suggested that chlorogenic acid and rutin in LBLF had low stability during the gastrointestinal digestion in vitro. Our study suggests that LBLF may show the instability in the contents of total flavonoids and some main monomers, but an enhancement in the antioxidant activity during gastrointestinal digestion, providing a reference for the stability improvement of LBLF in the next step.

中文翻译：

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枸杞叶黄酮类化合物在体外胃肠道消化过程中的抗氧化活性和稳定性

摘要 本研究考察了枸杞叶黄酮提取物（LBLF）在体外模拟口腔和胃肠道消化过程中的稳定性，包括总黄酮含量（TFC）、主要单体组成和抗氧化活性。在依次通过模拟口腔液（SOF）、胃液（SGF）和肠液（SIF）消化期间，在不同时间点测定冻干消化液样品中LBLF的TFC。结果表明，与初始 TFC 811.72 ± 0.72 mg RE/g DW 相比，总黄酮在口服消化过程中没有显着变化，而在胃消化阶段（p < 0.05）明显增加，此时 pH 值最低。消化系统，表明胃蛋白酶、胰蛋白酶促进了 LBLF 中黄酮类物质的释放，和胆汁，然而在肠道消化过程中减少可能是由于 LBLF 在弱碱性介质中的不稳定性。此外，SGF 和 SIF 消化显着提高了 LBLF 的抗氧化能力和生物可及性（p < 0.05）。胃消化后液体样品对自由基的清除作用依次为O2 − · > ABTS+ · > DPPH > ·OH > FRAP，而肠道消化样品的清除作用表现为ABTS+ · > O2 − · > DPPH > FRAP > ·哦。高效液相色谱 (HPLC) 结果表明 LBLF 中的绿原酸和芦丁在体外胃肠道消化过程中稳定性较低。我们的研究表明，LBLF 可能表现出总黄酮和一些主要单体含量的不稳定性，