Gracilaria chorda-derived compounds improve lipid metabolism and insulin sensitivity in 3T3-L1 adipocytes and high-fat diet-induced obese zebrafish larvae

Objective: To isolate and identify active constituents from Gracilaria chorda extract prepared under subcritical water conditions at 210 °C (GCSW210) and evaluate their anti-obesity and anti-diabetic effects in 3T3-L1 adipocytes and high-fat diet (HFD)-induced obese zebrafish larvae. Methods: GCSW210 was fractionated through solvent partitioning, ion-exchange chromatography, and silica gel medium-pressure liquid chromatography, followed by preparative high performance liquid chromatography. At each step, bioactivities were assessed in 3T3-L1 adipocytes by Oil Red O staining and 2-NBDG uptake assays. The most active fractions were further purified, and isolated compounds were tested in HFD-induced obese zebrafish larvae. Results: Liquid chromatography-hyphenated analysis with reference standards identified two major compounds in GCSW210: 5-hydroxymethylfurfural and bis(5-formylfurfuryl) ether. Both compounds significantly inhibited lipid accumulation in 3T3-L1 adipocytes and modulated gene expression associated with adipogenesis, glucose metabolism, and inflammation in zebrafish. They also enhanced glucose uptake, reduced circulating glucose levels, and improved insulin sensitivity. Notably, the effects were comparable to those of the crude GCSW210 extract. In silico docking studies confirmed stable interactions of both compounds with key metabolic and inflammatory targets, with bis(5-formylfurfuryl) ether showing stronger binding affinities. Conclusions: These findings suggest that 5-hydroxymethylfurfural and bis(5-formylfurfuryl) ether are key contributors to the therapeutic activity of Gracilaria chorda , highlighting its potential as a functional food ingredient for the prevention or management of metabolic disorders.