Co-production of high-purity floridoside and isofloridoside ameliorates MASH via Parabacteroides goldsteinii-UDCA-FXR enterohepatic axis

BACKGROUND: Metabolic dysfunction-associated steatohepatitis (MASH), the progressive form of metabolic dysfunction-associated fatty liver disease (MAFLD), is tightly linked to gut microbiota dysbiosis and disrupted bile acid (BA) homeostasis. Floridoside (Flor), a marine glycoside from the edible seaweed Pyropia haitanensis (P. haitanensis), exerts promising biological activities. However, protocols for its high-purity preparation and the mechanisms underlying its anti-MASH effects remain unclear. PURPOSE: To develop a protocol for the preparation of high-purity Flor and its isomer isofloridoside (Isoflor) from P. haitanensis, and to elucidate how Flor alleviates MASH via regulating gut microbiota and BA metabolism. METHODS: High-purity Flor and Isoflor were isolated via integrated chromatography, with their chemical structures confirmed by LC-MS and NMR. Anti-MASH efficacy was evaluated in a high-fat diet (HFD)-induced murine MASH model. The underlying mechanisms were explored using multi-omics analyses, including transcriptomics, gut microbiota metagenomics and BA-targeted metabolomics, and further validated by molecular docking, molecular dynamics simulation and western blotting; the compounds' biosafety was evaluated using zebrafish. RESULTS: High-purity Flor and Isoflor were successfully isolated, each with a purity of ≥ 99.0%. Both compounds exhibited a favorable biosafety profile and comparable lipid-lowering activity in zebrafish. In HFD-induced murine MASH models, Flor robustly ameliorated HFD-driven obesity, hepatic steatosis, and chronic inflammation, and restored systemic BA homeostasis characterized by a markedly increased non-12-OH/12-OH BA ratio. Meanwhile, Flor treatment dramatically enriched the relative abundance of intestinal Parabacteroides goldsteinii (P. goldsteinii), which showed a significant positive correlation with MASH alleviation and beneficial BAs (e.g., ursodeoxycholic acid (UDCA)). Mechanistically, UDCA exerted its therapeutic effects by antagonizing FXR signaling, upregulating the hepatic protein and mRNA expression of CYP7B1 and CYP27A1, and ultimately promoting the activation of the alternative BA synthesis pathway. CONCLUSION: High-purity Flor and Isoflor were obtained via an integrated co-production process from P. haitanensis. We hypothesize that Flor may ameliorate MASH by enriching P. goldsteinii and modulating the UDCA-FXR axis to activate the alternative bile acid synthesis pathway, positioning Flor as a promising prebiotic candidate for MASH management.