Preparation and Immunomodulatory Function of Tiger Nut Meal Peptides

Tiger nut (Cyperus esculentus L.) meal peptides (TMP) are bioactive peptides prepared by hydrolyzing tiger nut meal-a by-product of tiger nut oil extraction-with alkaline protease. These peptides have demonstrated promising immunomodulatory potential. In this study, proteins were extracted from tiger nut meal using the alkali dissolution and acid precipitation method. The enzymatic hydrolysis conditions were then optimized through single-factor experiments and response surface methodology. The optimal hydrolysis conditions were determined as follows: hydrolysis time 4 h, pH 10, enzyme dosage 9000 U/g, and temperature 46°C. Under these conditions, the degree of hydrolysis reached (24.87 ± 0.91%). Subsequently, a peptide fraction with a molecular weight of < 3 kDa was obtained via ultrafiltration. In vitro, this fraction significantly promoted the proliferation of mouse splenic lymphocytes and induced the secretion of pro-inflammatory cytokines, including interleukin-2 (IL-2), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α). In vivo experiments showed that TMP effectively improved immune function in cyclophosphamide (CTX)-induced immunosuppressed mice, as indicated by increased immune organ indices, elevated serum levels of both pro-inflammatory cytokines (IL-2, IFN-γ, and TNF-α) and the anti-inflammatory cytokine interleukin-4 (IL-4), and alleviated histopathological damage in spleen tissue. This study provides theoretical support for the development of TMP in immunomodulatory products and expands the potential application of tiger nut by-products in the functional food industry.