Antitumor and Immunomodulatory Effects of Xylan Isolated from Passion Fruit (Passiflora edulis) Peel in Walker 256 Tumor-Bearing Rats

Chemotherapy remains one of the main therapeutic approaches for cancer treatment; however, its clinical use is frequently limited by significant adverse effects that compromise patients' quality of life and treatment adherence. Consequently, there is growing interest in identifying adjuvant therapies that are both effective and associated with fewer side effects. In this context, bioactive polysaccharides derived from native plants have emerged as promising candidates because of their antitumor properties and low toxicity. These compounds can suppress tumor progression by modulating the immune response. This study aimed to chemically characterize the insoluble dietary fiber (IDF) isolated from yellow passion fruit (Passiflora edulis) peel and evaluate its antitumor activity, as well as its immunomodulatory effects on peritoneal macrophages and splenic T lymphocytes. Antitumor activity was evaluated in vivo using the Walker 256 tumor model in male Wistar rats treated for 14 days before and after tumor inoculation. Tumor growth, final tumor volume, and tumor weight were assessed. Macrophage activity was evaluated by measuring phagocytic capacity, secretory vesicle formation, and hydrogen peroxide production. Splenic lymphocyte viability was determined using the Alamar Blue assay following stimulation with concanavalin A (ConA) or lipopolysaccharide (LPS) as mitogens. A linear (1→4)-β-D-xylan was isolated from the insoluble dietary fiber fraction and significantly reduced tumor growth rate (1.5-fold), overall tumor burden (3-fold reduction in the area under the growth curve), and final tumor weight (2-fold) compared with tumor-bearing controls. Treated animals also exhibited reduced phagocytic activity (1.6-fold), secretory vesicle formation (1.3-fold) and hydrogen peroxide production (1.8-fold) in relation to tumor-bearing controls. Additionally, the viability of both T and B splenic lymphocytes after ConA and LPS stimulation increased by 1.3-fold and 1.4-fold, respectively. The intake of xylan from insoluble dietary fiber obtained from passion fruit peel significantly reduced tumor size and modulated the immune response. Xylan intake reduced the phagocytic activity, secretory vesicle formation, and hydrogen peroxide production of peritoneal macrophages to levels comparable to those observed in the non-tumor-bearing control group, possibly as a consequence of reduced exposure to tumor-derived chemical mediators. Furthermore, the increased viability of splenic T and B lymphocytes compared with the tumor-bearing control group suggests that xylan may also modulate the adaptive immune response. The xylan obtained from passion fruit peel exhibited antitumor activity and modulated the immune response. Treatment reversed tumor-induced alterations in macrophage function and increased the viability of activated splenic T and B lymphocytes. These findings suggest that this xylan represents a promising candidate for use as an adjuvant in cancer treatment.