Anti-inflammatory effects of high phenolic compounds on raw 264.7 macrophage cells: Structure, identification, biological activity and cytokine regulation of gallic, syringic, vanillic, ferulic and p-coumaric acids, quercetin, egcg and ellagic acid

High phenolic compounds (HPC) are widely studied as anti-inflammatory agents, but the data on individual compounds in macrophages are scattered. This review focuses on eight HPC: gallic, syringic, vanillic, ferulic and p-coumaric acids, quercetin, epigallocatechin gallate (EGCG) and ellagic acid. We describe their structures and phenolic hydroxyl groups, their natural and synthetic sources, and the methods used for chemical identification (HPLC-DAD, LC-MS/MS, GC-MS and NMR). We then summarize their antioxidant, enzyme-inhibitory and antimicrobial activities and critically evaluate their effects on nitric oxide, prostaglandin E2 and the pro-inflammatory cytokines TNF-α, IL-6 and IL-1β in LPS-stimulated RAW 264.7 macrophages, together with Western blot evidence for iNOS, COX-2, NF-κB, MAPK and Nrf2/HO-1 signaling. The strongest and most consistent evidence in RAW 264.7 cells exists for EGCG, quercetin, ellagic acid and ferulic acid. For gallic, syringic, vanillic and p-coumaric acids the evidence rests largely on derivatives, extracts or other models, and some findings conflict, for example the induction of COX-2 by EGCG. Assay artefacts (H₂O₂ formation in medium, MTT reduction), the use of a single murine cell line and high µM concentrations limit the interpretation. Four tables, four figures and a graphical abstract summarize the evidence, and a standardized workflow is proposed in which identity and purity are verified before all eight compounds are tested under identical conditions.