The contents of total phenolics (TPC), individual phenolic acid and antioxidant activities in the free and bound fractions of potato with different flesh colors were systematically investigated. The TPC and antioxidant capacity in the bound fraction was significantly lower than that in the free fraction. Chlorogenic acid, neochlorogenic acid, cryptochlorogenic acid, caffeic acid, p-coumaric acid and ferulic acid were detected in the free fraction with chlorogenic acid being the most predominant, accounting for 35.21–81.78% of the total content. Caffeic acid, p-coumaric acid and ferulic acid were detected in the bound fraction in the colored potato with caffeic acid being the major one. In the free fraction, the content of each individual phenolic acid had positive correlation with antioxidant activity. In the bound fraction, caffeic acid and p-coumaric acid showed positive correlation with antioxidant activity. This study promotes further understanding of the correlations among TPC, phenolic acids and antioxidant activity.

Anthocyanin-rich extracts have shown anti-inflammation activity in mouse colitis models. Cyanidin-3-glucoside (C3G) is one of the widespread anthocyanins in plants, and cyanidin (Cy) is the aglycone of C3G that can be generated in intestine under gut microorganism metabolism. To explore the anti-inflammatory activity of single anthocyanins compound and show the potential mechanism, the protective effects of C3G and its aglycone Cy on 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in mice and lipopolysaccharide (LPS)-stimulated Caco-2 cellular monolayer inflammation were studied. The results showed that both C3G and Cy significantly improved the clinical symptoms and relieved the histological damage in TNBS-challenged mice. The activity of myeloperoxidase and the excretion of inflammatory cytokines tumor necrosis factor-α, interleukin-1β, interleukin-6, and interferon-γ were also significantly inhibited at the administration dosage of 200 μmol/kg. In vitro studies showed that when LPS-stimulated Caco-2 cells were pretreated with C3G and Cy, the destruction of the intestinal epithelial barrier was ameliorated due to the improvement of the transepithelial electrical resistance and Lucifer yellow flux values, while there were no significant difference between C3G and Cy groups at the same dosage. Similarly, both C3G and Cy suppressed nitric oxide production and inflammatory cytokines secretion of LPS-induced Caco-2 cells. C3G and its aglycone Cy had similar anti-inflammatory activity in both colitis mice and Caco-2 cells. The results suggest that C3G and Cy may exert anti-inflammatory effects by protecting the intestinal barrier as well as by suppressing inflammatory cytokine secretion. Thus, C3G or Cy could be potential preventive agents or supplementary medicines for inflammatory bowel disease.