Protective Effect of Sweetpotato (Ipomoea batatas L.) Leaf Phenolic Acids Extract on IL-1β-Induced Barrier Injury of Caco-2 Monolayers

The status quo of a high-fat diet can impair the integrity of the intestinal barrier and promote inflammatory bowel diseases. The exploration of natural products as sources of new lead compounds that control such diseases becomes essential. Sweetpotato leaves (SPLs) have strong biological activity, and their phenolic acids were recently reported to be able to impart antioxidative, anti-inflammatory, and neuroprotection. The aim of this study was to investigate the effects and mechanisms of sweetpotato leaf phenolic acids (SPLPAs) extract on interleukin 1 beta (IL-1 beta)-induced barrier injury of Caco-2 monolayers. The safety from 0.02 to 0.2 mg/mL SPLPA extracts were demonstrated using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) method and Trypan blue staining. The 0.2 mg/mL SPLPA extract significantly decreased the release of Nitric oxide (NO) generation and its contribution to the expression of inflammation-related nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), and nuclear factor kappa B (NF-kappa B) were evaluated. Further investigation suggested that the SPLPA extract inhibited the IL-1 beta induced decrease in the transepithelial electrical resistance (TEER) value and could upregulate the IL-1 beta induced decline in tight junction protein levels. The results suggested that the SPLPA extract could enhance the integrity of Caco-2 monolayers. These results clarified the beneficial effects of SPLPA extract on inflammatory Caco-2 monolayers, indicating that the application of SPLPA extract in medicine and functional food has great potential for exploration.