Rhamnogalacturonan I-rich fractions from cherry tomatoes stimulate phagocytosis in RAW 264.7 macrophages

Tomato (Lycopersicon esculentum) is widely known for its beneficial effects on human health. To investigate the beneficial effects of polysaccharides from cherry tomato, cherry tomato polysaccharides (CTP) were prepared, the component sugars were analyzed, and the immunomodulatory activities in RAW 264.7 macrophages were assessed. CTP mainly contained arabinose (Ara) and galactose (Gal), suggesting that CTP might be enriched with an arabinogalactan (AG) moiety. The Ara and Gal present in CTP are likely components of AG-II (35.4%), namely arabino-β-(3,6)-galactan. To investigate the immunomodulatory activity of CTP, cytokine levels and iNOS2, COX-2, and NF-κB protein levels were analyzed, and NF-κB nuclear translocation and phagocytosis were observed by immunofluorescence. CTP significantly increased the levels of TNF-α, MCP-1, and IL-6. CTP also increased iNOS2 and COX-2 expression as well as NF-κB nuclear translocation in RAW 264.7 cells. CTP significantly stimulated phagocytosis activity. These results showed that CTP stimulates macrophage activity, which can boost the innate immune response. CTP with high AG-II content could be used as a prebiotic to strengthen immunity.