Nanoencapsulated Syzygium aromaticum oil alleviates acetic acid-induced ulcerative colitis in rats by influencing critical redox, NF-κB/iNOS, and Keap1/Nrf2/HO-1 signaling pathways.

Ulcerative colitis (UC) is an autoimmune inflammatory condition characterized by significant mucosal destruction. Although Syzygium aromaticum (Clove oil; CO) oil is well-known for its antioxidant and anti-inflammatory properties, its high volatility, toxicity, and hydrophobicity can compromise its biological efficacy. Therefore, nanoencapsulation is a feasible approach for boosting its therapeutic potential, including stability, bioavailability, and target delivery. Herein, this study was designed to minimize acetic acid-mediated UC using CO alone or encapsulated in nano-vehicles including PCL, CS, and ALG. The developed nano-capsules CO were characterized by Zetasizer, FT-IR, and SEM, and subsequently, the encapsulation efficiency and controlled release profile of CO were determined. Forty adult rats were assigned to five groups (n = 8) as follows: the control (CONT) group, which received dimethyl sulfoxide (DMSO) once daily; the UC group, which received rectal acetic acid (AA) instillation on day 8 of the experiment. CO group: rats were treated orally with clove oil (250 mg/kg) dissolved in DMSO once daily. PCL@CS + ALG group; rats were orally treated with nano-vehicle (250 mg/kg). CONPs group: rats received clove oil nanoparticles (PCL@CO(CS + ALG)NPs, 250 mg/kg). All groups received their respective treatments once a day for seven consecutive days, before and after UC induction. An in silico study revealed the binding affinities of eugenol, the principal bioactive constituent of CO, toward inflammatory molecules at both the mRNA and protein levels. Biologically, the colon outcomes showed that CO, either alone or loaded with nanoparticles (CONPs), significantly decreased MDA and NO levels and elevated antioxidant enzymatic activities (SOD, CAT, , GPx, and GR), with higher GSH levels. Additionally, the treatment of rats with CO or CONPs mitigated colon inflammation by decreasing the MPO activity, TNF-α, IFN-γ, IL-1β, and PGE2 levels, as well as downregulating the expression of NF-κB, IL-6, IL-8, and iNOS genes. Remarkably, CONPs prevented the colon oxidative damage by modulating the mRNA expression of Keap1/Nrf2/HO-1 signaling pathways. Unlike the rats exposed to AA, the treatment with CO and CONPs dramatically restored the mRNA expression of Cdc25c and RNF8 genes. Histologically, the CONPs-treated group showed a clear restoration of colonic tissue architecture toward normal, accompanied by normalization of VEGF and α-SMA immunoexpression patterns. Conclusively, CO, either alone or encapsulated in nanoparticles (CONPs), offers promising therapeutic potential for UC, likely through its anti-inflammatory, antioxidant, and anti-fibrotic effects, as well as superior regulation of angiogenesis compared with pure CO.