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.