Structural characterization of rhamnogalacturonan-I purified from Curcuma longa and its anti-lung cancer efficacy via immunostimulation

In this study, we investigated the structural characteristics, immunostimulatory activities, and anti-cancer effects of turmeric-derived polysaccharides (TPE-I). Several results related to the structural features revealed that TPE-I possesses a typical rhamnogalacturonan (RG)-I structure. Furthermore, macrophage cytokine secretion was significantly reduced by partial side chain and main chain cleavage of TPE-I via sequential enzymatic and chemical degradation. In contrast, the administration of TPE-I effectively enhanced the cytotoxic effects of natural killer (NK) cells and cytotoxic T lymphocytes against tumor cells. Additionally, the administration of TPE-I potently inhibited lung cancer induced by Colon26-M3.1, and this efficacy persisted even in mice with NK cell function blocked by anti-asialo GM1 antibody. Consequently, it was confirmed that TPE-I, a RG-I type polysaccharide purified from turmeric, has potent anticancer effects which are closely related to immunostimulation. The results of this study support the hypothesis that curcuminoids are not the only bioactive substances present in turmeric.