Immunomodulatory effects of polysaccharides from purple sweet potato on lipopolysaccharide treated RAW 264.7 macrophages

Immunomodulatory effects of water-soluble polysaccharide (WSP), dilute alkali-soluble polysaccharide (DASP), and concentrated alkali-soluble polysaccharide (CASP) from purple sweet potato were evaluated by using lipopolysaccharide (LPS) treated RAW264.7 macrophage cell models. Results showed WSP, DASP, and CASP (100, 200, and 400 μg/mL) could suppress abnormal phagocytosis, overproduction of TNF-α and IL-6, and abnormal apoptosis caused by LPS. The high doses (200 and 400 μg/mL) of DASP and CASP could distinctly reduce excessive NO production as compared with LPS treatment group. In addition, 400 μg/mL of WSP, DASP, and CASP treatment groups exhibited dramatic decrease in the overexpression of IL-1β stimulated by LPS. Moreover, 200 and 400 μg/mL of WSP, DASP, and CASP markedly improved anti-inflammatory cytokine IL-10 as compared with LPS treatment group. Furthermore, 400 μg/mL of WSP and DASP treatments significantly increased the level of IL-10 in nonstimulated macrophages when compared with normal control group. Practical applications Purple sweet potato [Ipomoea batatas (L.) Lam] is one type of highly nutritional vegetable containing many vitamins, minerals, dietary fiber, anthocyanin, and polysaccharides. In addition, it is also one of health-promoting edible plant sources. Recently, polysaccharides have attracted extensive attentions due to their various biological activities. Our study reveals that polysaccharides extracted from purple sweet potato are effective in protecting macrophages damaged by lipopolysaccharide. Therefore, polysaccharides from purple sweet potato have anti-inflammatory efficacy. Thus, this study indicates the potential applications of purple sweet potato polysaccharides in functional food.