Tumor inhibitory effect via immunostimulating activities of a rhamnogalacturonan‐I‐rich polysaccharide isolated from turmeric (Curcuma longaL.)

In this study, a turmeric polysaccharide (TP-0) was isolated through hot water extraction and ethanol precipitation to produce a novel active polysaccharide from turmeric other than curcuminoids. TP-0 was found to be primarily composed of eight different monosaccharides, such as galactose (15.9%), galacturonic acid (15.2%), arabinose (11.4%), and rhamnose (9.7%), which are typical rhamnogalacturonan (RG)-I sugars. When stimulated with TP-0, peritoneal macrophages secreted a variety of immunostimulatory cytokines. In addition, intravenous and oral administration of TP-0 significantly enhanced the natural killer (NK) cells and cytotoxic T lymphocyte (CTL)-mediated cytotoxicity against tumor cells. In an assay for lung cancer induced by Colon26-M3.1 carcinoma, prophylactic intravenous and oral administration of TP-0 effectively inhibited lung cancer. These findings reveal that TP-0, a typical RG-I-type polysaccharide that is isolated from turmeric, has potent anti-metastatic activities, and these activities are linked to various immunological factors such as macrophages, NK cells, and CTL. Practical applications Many studies related with turmeric have only focused that a curcuminoid of turmeric has beneficial effects on human health system. Nevertheless, in this study, it was confirmed that polysaccharide isolated from turmeric showed potent anti-cancer effects via activities of various immunological factors such as macrophages, NK cells, and CTL. These results suggest the high potential for development value of turmeric as a new candidate for immunostimulating-related health functional food ingredients.