Guaijaverin, a guava-derived flavonoid, attenuates high-fat diet-induced MASLD via regulating the gut microbiota–SCFA–ferroptosis axis

Guaijaverin (GUA), a guava-derived bioactive flavonoid, is a promising candidate for the development of functional foods targeting metabolic disorders. This study investigated the protective effects and underlying mechanisms of GUA against high-fat diet (HFD)-induced metabolic dysfunction-associated steatotic liver disease (MASLD), with particular emphasis on the gut-liver axis. Using an HFD-fed mouse model and free fatty acid (FFA)-stimulated AML12 hepatocytes, we integrated hepatic phenotypic evaluation, 16S rRNA sequencing, short-chain fatty acid (SCFA) quantification, antibiotic-mediated microbiota depletion, sodium butyrate supplementation, RSL3 rescue experiments, and hepatic transcriptomic analysis. GUA markedly alleviated hepatic steatosis, improved serum and hepatic lipid accumulation, and reduced liver injury. GUA also restored intestinal barrier integrity, reshaped gut microbiota composition, enriched SCFA-associated bacteria, and increased fecal SCFA levels. Antibiotic depletion attenuated the hepatoprotective effects of GUA, whereas butyrate supplementation partially restored these effects, supporting the involvement of gut microbiota-derived butyrate in GUA-mediated liver protection. Liver transcriptomic analysis further identified glutathione metabolism as a major pathway activated by GUA. Consistently, GUA restored redox homeostasis, reduced iron overload and lipid peroxidation, and maintained the GPX4-mediated anti-ferroptotic defense axis. These effects were weakened by microbiota depletion and partially rescued by butyrate supplementation. In AML12 hepatocytes, pharmacological induction of ferroptosis with RSL3 partially abolished the protective effects of GUA or sodium butyrate, further supporting ferroptosis inhibition as a functional downstream mechanism. Collectively, these findings indicated that GUA ameliorated HFD-induced MASLD, at least in part, through coordinated modulation of the gut microbiota-SCFA-ferroptosis axis, highlighting its potential as a guava-derived functional food ingredient for metabolic liver health.