Redox Reprogramming of the Diseased Liver by Dietary Flavonoids: From Molecular Signalling to Gut–Liver Crosstalk

Liver diseases, including fatty liver, hepatitis, and cirrhosis, remain major global health challenges due to their disruption of metabolic homeostasis and detoxification processes. Redox imbalance plays a central role in liver disease progression by promoting inflammation, hepatic stellate cell activation, mitochondrial dysfunction, and fibrogenesis. Although flavonoids have historically been considered direct reactive oxygen species (ROS) scavengers, emerging evidence indicates that their biological effect at physiological concentrations are primarily mediated through modulation of intracellular redox signalling rather than simple radical neutralisation. This review highlights flavonoids as redox-modulating agents capable of restoring hepatic redox homeostasis through coordinated regulation of molecular pathways. Mechanistically, flavonoids activate the Nrf2-Keap1 axis to enhance endogenous antioxidant defences, including heme oxygenase-1 and glutathione biosynthesis enzyme, while suppressing NF-κB-mediated pro-inflammatory signalling and modulating MAPK and PI3K/Akt pathways. They also regulate mitochondrial redox balance, supporting mitophagy, metabolic adaptation, and cellular resilience to oxidative stress. In addition, flavonoid biotransformation by the gut microbiome improves intestinal barrier integrity, reduces endotoxin-driven hepatic inflammation, and contributes to gut-liver crosstalk. Collectively, these mechanisms position dietary flavonoids as multi-target redox modulators with promising therapeutic potential in chronic liver disease, although further studies are needed to improve their bioavailability and clinical translation.