Structural Characterization and Antioxidant Activity of a Crude Polysaccharide from Cannabis sativa Leaves

As a traditional Chinese herbal medicine, Cannabis sativa holds broad prospects for application in the development of functional foods, pharmaceutical formulations, dietary supplements, and cosmetic products. However, the bioactivity of polysaccharides in C. sativa has been largely overlooked. In this study, crude C. sativa leaf polysaccharide (CSLP) was extracted using the hot-water extraction and ethanol-precipitation method. CSLP contains 64.15 ± 1.96% carbohydrates and 2.13 ± 0.47% protein, with a yield of 6.71 ± 0.84% (w/w). Preliminary structural characterization showed that CSLP was mainly composed of arabinose, galactose, and glucose, with a molecular weight of 28.867 kDa. CSLP not only demonstrated potential in vitro antioxidant activity against ABTS, DPPH, superoxide anion, and hydroxyl radicals, but also repaired H₂O₂-induced oxidative damage in RAW 264.7 macrophages by increasing the cellular levels of SOD, CAT, and GSH-Px, and reducing MDA levels. Mechanistically, CSLP possibly modulated the Nrf2/Keap1 signaling pathway in H₂O₂-stimulated RAW 264.7 cells via upregulating the gene expressions of Nrf2, NQO1, and HO-1, while downregulating Keap1 expression. These results suggest that CSLP could potentially be used as an antioxidant ingredient in the food, pharmaceutical, and cosmetic industries.