Anti-Adipogenic Effect of Secondary Metabolites Isolated from Tetracera loureiri on 3T3-L1 Adipocytes

A species of the genus Tetracera has been used as herbal medicine in traditional Indian Tetracera loureiri medicine. Tetracera loureiri, a plant from the Dilleniaceae family is considered one of the most valuable herbs in Thailand and is native to Southeast Asia. However, the anti-obesity effects of Tetracera loureiri extract have not been reported. In this study, we screened the effect of EtOH extract on lipid accumulation in a 3T3-L1 adipocyte model at various concentrations using Oil Red O staining, and the results were visualized under a light microscope. The fractionation of the soluble CH₂Cl₂ and EtOAc fractions from the EtOH extract revealed that both fractions significantly inhibited lipid accumulation in adipocytes at 2.5, 5, and 10 μg/mL, compared to n-hexane, n-BuOH, and aqueous extracts. Bioactivity-guided fractionation of the CH₂Cl₂ and EtOAc extract led to the phytochemical investigation of 10 secondary metabolites (1-10), and the structure of these compounds was identified using various spectroscopic methods. All isolated compounds were evaluated for their ability to inhibit adipogenesis at a concentration of 2.5, 5, and 10 μM compared with positive control (Orlistat 100 μg/mL); in particular, compounds 1-3, 5, and 7-8 showed 57.39 ± 6.98, 19.35 ± 4.53%, 75.81 ± 1.75%, 17.61 ± 1.62%, 19.83 ± 5.27 and 14.66 ± 3.85% reduction in fat accumulation at 10 μMm in 3T3-L1 adipocytes, respectively. The activity of these compounds also inhibited the secretion of adiponectin and leptin in 3T3-L1 adipocytes, suggesting their role in disrupting adipocyte function and metabolic regulation. Therefore, the results herein provide experimental evidence supporting the potential of Tetracera loureiri extracts as an anti-obesity therapeutic agent.