Study on immunostimulatory activity and extraction process optimization of polysaccharides from Caulerpa lentillifera

•We studied the process of extracting CLP by single factor experiment and response surface methodology.•The CLP with a concentration of 6.25–50 μg/mL significantly promoted the proliferation of RAW264.7 cells without showing toxic effects.•CLP significantly stimulated the phagocytosis of RAW264.7 and showed a dose-dependent effect, and significant changes in the morphology of macrophages.•CLP effectively increased the synthesis and secretion of cytokines (IL-6, TNF-α, IL-1β, and NO). The process of extracting polysaccharides from the green algae Caulerpa lentillifera was studied by single factor experiments and response surface methodology. Additionally, the immunostimulatory activity of Caulerpa lentillifera polysaccharides (CLP) on RAW264.7 mouse macrophage was evaluated by in vitro cell experiments. The results showed that the optimal extraction conditions consisted of ultrasonification for 30 min, extraction time of 9 h, extraction temperature of 100 °C, and a ratio of water to raw material of 40:1. RAW264.7 macrophage exhibited enhanced phagocytosis with no toxic effects after treatment with CLP. In addition, CLP effectively increased the synthesis and secretion of cytokines (IL-6, TNF-α, IL-1β, and NO), whereby the secretion levels of IL-6, TNF-α, and IL-1β were 1,840.32 ± 21.03 pg/mL (50 μg/mL), 197.17 ± 3.13 ng/mL (50 μg/mL), and 1,178.35 ± 78.82 pg/mL (25 μg/mL), respectively. The polysaccharides contained in Caulerpa lentillifera have potential value for further development due to their immunological activity.