Novel PPAR-γ Agonist from the Soft Coral Sarcophyton crassocaule: Modulating Glucose Uptake and Lipid Droplet Formation

Two previously undescribed highly oxygenated cembrane-type diterpenes, namely sarcocraol A (1) and sarcocraol B (2), along with five known compounds (3-7), have been isolated from the soft coral Sarcophyton crassocaule collected off Ximao Island in the South China Sea. Their structures were determined through comprehensive spectroscopic analysis, QM-NMR calculations, TDDFT-ECD computation, X-ray diffraction analysis, and by comparison with literature data. Plausible biosynthetic pathways for these compounds were also proposed. All compounds were evaluated for peroxisome proliferator-activated receptors (PPARs) transcriptional activity using luciferase assay. The bioassay results demonstrated that compound 1 exhibits selective PPAR-γ agonistic activity. Furthermore, it promoted glucose uptake in HepG2 cells by 1.18-, 1.45-, and 1.90-fold at concentrations of 2.5, 5, and 10 μM, respectively, whereas rosiglitazone (10 μM) produced a 2.47-fold increase over the induced control. Compound 1 at 10 μM induced mild lipid accumulation in 3T3-L1 cells, showing a 1.63-fold increase relative to the control, which was much lower than the 3.28-fold increase observed in rosiglitazone (10 μM) group indicating its potential antidiabetic properties. These findings suggested that compound 1 could be a promising lead for the development of antidiabetic agents.