Anti-inflammatory activity of Zanthoxylum rhetsa bark fractions via suppression of nuclear factor-kappa B in lipopolysaccharide-stimulated macrophages

Background: Zanthoxylum rhetsa is a plant used in traditional medicine and is known to possess health benefits such as antibacterial, antidiabetic, and anti-diarrheal activities. 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.