Abstract: Lycium barbarum L. is traditionally used as a medicinal and food resource in China. Spray dried powder of its fresh fruits is widely used as a food product or a functional food ingredient. In this study, the immunoregulatory effects of Lycium barbarum L. powder (LB), Lycium barbarum L. polysaccharides (LBP) and their mixture (LB + LBP) on cyclophosphamide (CTX)-induced immunosuppressive mice were investigated, as well as their influences on gut microbiota homeostasis. The results showed that LB, LBP and their combination restored the body mass and food intake of immunosuppressed mice to different degrees, improved spleen, thymus and colon injury, effectively promoted the secretion of cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interferon-γ (IFN-γ) and immunoglobulin (Ig) A in immunosuppressed mice, regulated the expression of immune-related genes in the colon, promoted the generation of short chain fatty acids (SCFAs), significantly modulated the relative abundance of Muribaculaceae_unclassified, Muribaculum, Mucispirillum, Helicobacter, Bilophila and Clostridiales (P < 0.05), and reversed the abnormal metabolic function of the gut microbiota induced by CTX. Moreover, compared with LBP, LB and LB + LBP decreased the relative abundance of Clostridiales and increased the relative abundance of the beneficial bacterium Duncaniella, and LB + LBP also decreased the relative abundance of Anaerotruncus. The results of this study will provide a theoretical basis for the research and development of specific health products and diversified products in the Lycium barbarum L. processing industry.

Key words: Lycium barbarum L.; immunity; gut microbiota; polysaccharides; metabolic function