Coptis chinensis alkaloids exert anti-adipogenic activity on 3T3-L1 adipocytes by downregulating C/EBP-α and PPAR-γ

Obesity is a complex, multifactorial, and chronic disease that increases the risk for type 2 diabetes, coronary heart disease and hypertension, and has become a major worldwide health problem. Developing novel anti-obesity drugs from natural products is a promising solution to the global health problem of obesity. While screening anti-obesity potentials of natural products, the methanol extract of the rhizome of Coptis chinensis (Coptidis Rhizoma) was found to significantly inhibit adipocyte differentiation and lipid contents in 3T3-L1 cells, as assessed by Oil-Red O staining. Five known alkaloids, berberine, epiberberine, coptisine, palmatine, and magnoflorine, were isolated from the n-BuOH fraction of the methanol extract of Coptidis Rhizoma. We determined the chemical structure of these alkaloids through comparisons of published nuclear magnetic resonance (NMR) spectral data. Furthermore, we screened these alkaloids for their ability to inhibit adipogenesis over a range of concentrations (12.5-50 μM). All five Coptidis Rhizoma alkaloids significantly inhibited lipid accumulation in 3T3-L1 cells without affecting cell viability in a concentration dependent manner. In addition, the five alkaloids significantly reduced the expression levels of several adipocyte marker genes including proliferator activated receptor-γ (PPAR-γ) and CCAAT/enhancer-binding protein-α (C/EBP-α). In the present study, we found that the isolated alkaloids inhibited adipogenesis in a dose-dependent manner in 3T3-L1 cells; this inhibition was attributed to their abilities to downregulate the protein levels of the adipocyte marker proteins PPAR-γ and C/EBP-α. Thus, these results suggest that Coptidis Rhizoma extract and its isolated alkaloids may be of therapeutic interest with respect to the treatment of obesity.