Physicochemical properties, antioxidant and anti-inflammatory activities of polysaccharides from lotus leaves by pectinase-assisted extraction

In order to improve the extraction yield of lotus leaf polysaccharide (LLP) and offer scientific foundation for utilization of LLPs in the food and pharmaceutical industries, pectinase-assisted extraction method was employed for the preparation of LLP. The chemical composition, physicochemical properties (e.g. rheological and thermal properties etc.), antioxidant and anti-inflammatory effects of LLP and its two purified fractions (LLP1 and LLP3) obtained using DEAE-52 and subsequent Sephadex G-100 column chromatography were also investigated. Antioxidant assays indicated that the polysaccharides had remarkable DPPH center dot and ABTS+center dot scavenging activities. In H2O2-induced RAW264.7 cells, LLPs showed marked protective effect on oxidative stress, reducing the MDA and ROS contents and increasing the CAT and SOD activities. LLPs were also found to effectively modulate the expressions of CAT, SOD1, Nrf-2, HO-1, NQO1 and Keap1 mRNA. Thus, the potent antioxidant effects of LLPs were achieved possibly by regulating the Keap1/Nrf-2/HO-1 signaling pathways. In lipopolysaccharide-treated RAW264.7 macrophages, LLPs reduced phagocytic ability, decreased release of NO, TNF-alpha, IL-1 beta and IL-6, and increased release of IL-10 and TGF-beta 1, indicating their potent anti-inflammatory effect. LLPs down- regulated expressions of iNOS, IL-1 beta, IL-6, TNF-alpha, COX-2, and TLR-4 mRNA. Therefore, modulation of NF-kappa B signaling pathway is possibly the important anti-inflammatory mechanism of LLPs.