Effect of arabinoxylan- and rhamnogalacturonan I-rich polysaccharides isolated from young barley leaf on intestinal immunostimulatory activity

Four polysaccharide fractions were prepared from barley leaves and then in vitro intestinal immunostimulatory activity was compared. Among fractions, high molecular weight fraction prepared by enzyme extraction, namely BLE-P, showed the potent in activating bone marrow cell proliferation through Peyer's patch (PP), and in stimulating cytokine production in in vitro. By performing monosaccharide composition analysis, BLE-P was identified as a mixture of hemicellulosic glucuronoarabinoxylan and pectic rhamnogalacturonan I accounting for above 80%. Subsequently, BLE-P was orally administered to mice for 20 days to investigate the effect on the in vivo intestinal immunostimulatory activity. BLE-P administration not only augmented the production of immunoglobulin A (IgA), but also increased the levels of IgA-related cytokines, such as transforming growth factor-β and interleukin-10. These results suggest that BLE-P is most likely to facilitate the production of IgA via induction of various IgA-producing cytokines in small intestinal immune system.