Anti-inflammatory activity of nonyl 8-acetoxy-6-methyloctanoate, isolated from the cultured marine diatom, Phaeodactylum tricornutum : mediated via suppression of inflammatory mediators in LPS-stimulated RAW 264.7 macrophages

In this study, the anti-inflammatory effects of nonyl 8-acetoxy-6-methyloctanoate (NAMO), isolated from the cultured marine diatom, Phaeodactylum tricornutum Bohlin, against LPS-induced RAW 264.7 macrophages were evaluated. NAMO has indicated the strongest inhibitory effects against nitric oxide (NO) and prostaglandin E₂ (PGE₂) production, dose-dependently, on lipopolysaccharide (LPS)-induced RAW 264.7 cells. The 50% NO production inhibitory concentration (IC₅₀) of NAMO was 24.8 µM with the least cytotoxic effect in both LDH and MTT assays. Inflammatory stimulators such as LPS, which induce cytokines in the process of macrophage activation and mediate tissue response in different phases of inflammation, were studied. NAMO showed significant and strong suppression of pro-inflammatory cytokine and interleukin-1β (IL-1β) production, but no significant inhibitory effect on the production of cytokines including tumor necrosis factor-α (THF-α) and interleukin-6 (IL-6) at the tested concentrations against LPS treatment on RAW macrophages. Western blot analysis was carried out to determine the protein expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins which mediate the suppression effect of NAMO on NO and PGE₂ production. The Western blot assay confirmed the suppression of iNOS and COX-2 protein expressions against LPS-stimulated RAW264.7 cells. Collectively, NAMO isolated from the cultured marine diatom, P. tricornutum exhibited a profound anti-inflammatory effect in vitro, suggesting that the compound might have a beneficial effect during the treatment of inflammatory diseases and can be used in functional food applications.