Anti‑inflammatory Activity of Zanthoxylum rhetsa Bark Fractions via Suppression of Nuclear Factor‑kappa B in Lipopolysaccharide‑Stimulated Macrophages

Objectives: The objective of this study was to explore and demonstrate the anti‑inflammatory activity of various solvent fractions of Z. rhetsa bark. Materials and Methods: The effect of crude methanolic extract and its fractions (hexane, chloroform, ethyl acetate, and butanol) on the levels of pro‑inflammatory cytokines (interleukin‑1β, tumor necrosis factor‑alpha, and interleukin‑6) and inflammatory factors was tested via targeting nuclear factor‑kappa B (NF‑κB) signaling pathways in lipopolysaccharide (LPS)‑stimulated mouse RAW 264.7 macrophages. Results: Treatment with all the solvent fractions at various concentrations (50, 100, and 200 µg/ml) suppressed pro‑inflammatory cytokine levels in a dose‑dependent manner. Among the fractions, the chloroform fractions exhibited a significant inhibition of LPS‑induced inflammation. Moreover, these fractions effectively suppressed the expression of various NF‑κB signaling targets, including NF‑κB, nitric oxide synthase, and cyclooxygenase‑2 as well as inhibited the degradation of nuclear factor of kappa light polypeptide gene enhancer in B‑cell inhibitor, alpha (inhibitor of kappa B alpha [IκBα]). This anti‑inflammatory effect was mediated by the prevention of IκBα degradation, as this protein prevents the translocation of NF‑κB from the cytoplasm to the nucleus, initiating the transcription of pro‑inflammatory genes. Conclusion: Thus, the Z. rhetsa chloroform fraction may be an effective natural anti‑inflammatory agent against inflammation‑associated diseases.