Applied Science and Technology, North Carolina Agricultural and Technical State University, Greensboro, NC 27411, USA.
Department of Food Science, University of Arkansas, Fayetteville, AR 72704, USA.
Nutrients. 2024 Oct 24;16(21):3609. doi: 10.3390/nu16213609.
Obesogenic diets cause intestinal inflammation and dysfunction. Polyphenols have shown a positive impact on reducing inflammation in in vitro studies. However, their bioactivity may not be the same in the in vivo system due to structural alteration by the gastrointestinal digestive process. The purpose of this study was to investigate the anti-inflammatory effect of onion peel and its major bioactive compound, quercetin, in the intestine and further examine the impact of intestinal digestion on this effect.
Onion peel extract (OPE) and quercetin (Q) were digested using gastrointestinal digestive enzymes in vitro and then treated into lipopolysaccharide (LPS)-stimulated Caco-2/HT-29 cells. Genes and proteins related to tight junction, inflammation, and epithelial integrity were measured.
OPE and digested OPE (DOPE) had a higher protective effect on LPS-induced tight junction and inflammatory genes and paracellular permeability than Q and digested Q (DQ). DOPE was more effective than OPE, while digestion did not change the activity of Q. The anti-inflammatory effect of OPE and Q with or without digestion was achieved by inhibiting nuclear factor kappa B through AMP-activated protein kinase-activated silent mating-type information regulation 2 homolog 1.
It was the first to find that a crude extract, after undergoing gastrointestinal digestion, demonstrated a notably superior anti-inflammatory effect in the cell study, suggesting the consumption of onion peels could potentially yield similar benefits in the human intestine. This discovery underscores the potential of onion peel polyphenols in combating intestinal inflammation, making them a compelling area of research for future therapeutic applications using food byproducts.
致肥胖饮食会引起肠道炎症和功能障碍。多酚在体外研究中已显示出对减轻炎症有积极影响。然而，由于胃肠道消化过程中结构的改变，它们的生物活性在体内系统中可能并不相同。本研究旨在探讨洋葱皮及其主要生物活性化合物槲皮素在肠道中的抗炎作用，并进一步研究肠道消化对这种作用的影响。
采用胃肠道消化酶对洋葱皮提取物（OPE）和槲皮素（Q）进行体外消化，然后用脂多糖（LPS）刺激 Caco-2/HT-29 细胞处理。测量与紧密连接、炎症和上皮完整性相关的基因和蛋白质。
OPE 和消化的 OPE（DOPE）对 LPS 诱导的紧密连接和炎症基因以及旁细胞通透性的保护作用高于 Q 和消化的 Q（DQ）。DOPE 比 OPE 更有效，而消化并没有改变 Q 的活性。OPE 和 Q 无论是消化与否，通过 AMP 激活的蛋白激酶激活沉默交配型信息调节 2 同系物 1 抑制核因子 kappa B 来发挥抗炎作用。
这是首次发现经过胃肠道消化后的粗提物在细胞研究中表现出明显优越的抗炎作用，这表明食用洋葱皮可能在人体肠道中产生类似的益处。这一发现突显了洋葱皮多酚在对抗肠道炎症方面的潜力，使它们成为利用食物副产物进行未来治疗应用的一个引人注目的研究领域。
