Immunomodulatory effects of sea buckthorn leaf green tea in cyclophosphamide-induced immunosuppressed mice.

Sea buckthorn leaf green tea prepared from Hippophae rhamnoides L. leaves contains a complex mixture of bioactive phytochemicals, yet its immunoregulatory potential remains unclear. The study aimed to investigate the immunomodulatory effects and underlying mechanisms of sea buckthorn leaf green tea extract (SBGT) in cyclophosphamide-induced immunosuppressed mice. Widely targeted metabolomics revealed that green tea processing significantly increased the contents of flavonoids and polyphenols in sea buckthorn leaves. Animal experiments showed that SBGT effectively alleviated cyclophosphamide-induced atrophy of the thymus and spleen, restored the secretion of cytokines and immunoglobulins, and improved systemic immune function. Meanwhile, SBGT repaired intestinal mucosal damage, increased goblet cell numbers, and upregulated the expression of tight junction proteins ZO-1, Occludin, and Claudin, thereby enhancing intestinal barrier integrity. Furthermore, SBGT remodeled the gut microbiota structure by increasing the abundance of beneficial genera such as Muribaculaceae, Bacteroides, and Ligilactobacillus, promoting short-chain fatty acids production, and reversing gut microbial dysbiosis. Collectively, SBGT exerts significant immunomodulatory effects and can be used as a promising natural functional tea product.