Background and Purpose: Citri reticulatae Pericarpium Viride (CRPV), has multiple pharmacological activities. However, its polysaccharide components’ separation, purification and activity have not been reported. We aimed to isolate the polysaccharides from CRPV (CRPV-P) and explore its hepatoprotective effects against lipopolysaccharide (LPS)-induced acute liver injury (ALI). Experimental Approach: From the ethanol-precipitate of a water extract, a fraction (CRPV-P) was isolated by DEAE-cellulose-52 and sephadex G-75 gel chromatography. The physicochemical properties and structural characteristics of CRPV-P were analyzed. The anti-inflammation and hepatoprotective activities of CRPV-P were evaluated in the cellular and mice model of LPS-induced ALI, and the mechanism was investigated. Key Results: CRPV-P, a polysaccharide (220 kDa) purified from CRPV, primarily composed of arabinose, rhamnose and galacturonic acid. In LPS-induced THP-1, AML12 and HepG2 cells, it reduced TNF-α levels and suppressed hepatocyte apoptosis. In vivo, CRPV-P reversed the increased serum levels of ALT, AST and LDH, attenuated hepatic histopathological damage, and concurrently inhibited TNF-α overproduction and apoptosis in hepatocytes. With monophosphoryl lipid A (MPLA), a targeted agonist of Toll-like receptor 4 (TLR4), we found that the hepatoprotective activity of CRPV-P correlates with the inactivation of TLR4/MyD88/NF-κB and cell apoptosis pathway through restraining TLR4, impeding the inflammatory damage and hepatic injury caused by ALI. Conclusions and Implications: CRPV-P displays significant anti-inflammatory and hepatoprotective effects through inhibiting TLR4-mediated inflammatory/apoptotic signaling pathways in LPS-induced ALI. CRPV-P could be considered as a potential therapeutic candidate for ALI treatment.

Background and Purpose: Metabolic dysfunction-associated fatty liver disease (MAFLD) pathogenesis involves gut microbiota dysbiosis. This study investigated pseudolaric acid B (PAB), a diterpenoid from Pseudolarix kaempferi, for its therapeutic potential in high-fat diet-induced MAFLD mice. Experimental Approach: The effects of PAB on MAFLD were evaluated in a high-fat diet -induced C57BL/6J mouse model. The regulatory impact of PAB on the gut microbiota and metabolites was explored by 16s rRNA sequencing and metabolomics analysis. Fecal microbiota transplantation experiments further validated these results. Key Results: PAB treatment significantly improved body weight, liver index, serum biochemical indices, and histopathological damage in MAFLD mice. Gut microbiota analysis revealed PAB significantly reduced g_Faecalibaculum, g_Allobaculum, g_Ileibacterium, and g_Dubosiella abundance. Metabolomic profiling demonstrated PAB treatment increased the level of the microbiota-derived tryptophan metabolite, cinnabarinic acid (CA). The CA content was negatively correlated with the abundance of the four bacteria identified above. Fecal microbiota transplantation validated gut microbiota’s causal role in PAB’s therapeutic effects. Mechanistically, PAB activated the aryl hydrocarbon receptor (AhR)— CA’s target receptor— subsequently upregulating IL-22 expression and triggering JAK1/STAT3 signaling. This cascade suppressed key fatty acid synthesis regulators: SREBP-1c, ELOVL6, Acc, Fasn, and Scd1 at both mRNA and proten levels. Conclusion and Implications: PAB as a promising prebiotic agent against MAFLD through gut microbiota modulation, CA/AhR/IL-22 axis activation, and inhibition of hepatic lipogenesis pathways. The study elucidates a novel mechanism where microbial metabolite CA mediates PAB’s hepatoprotective effects via AhR — dependent signaling.