Black radish (Raphanus sativus L. var. niger) is a root vegetable that is distributed all over the world and it is used for folk medicine to treat jaundice, liver disease, indigestion and gastric pains. In the present study, we investigated the anti-obesity activity of black radish extract (BRE) by conducting various experiments. The inhibitory, dose dependent effect of BRE on adipogenesis was shown in 3T3-L1 preadipocytes with Oil Red O staining, and it effectively decreased the intracellular triglyceride concentration of adipocytes. The effect of BRE on the expression of various adipogenesis-related genes was analyzed via western blotting and quantitative real time PCR. We demonstrated that BRE significantly down regulated the expression of C/EBPα, C/EBPδ, PPARγ, aP2, SREBP-1c, ADD1, ACC, FAS, SCD, ATGL, HSL, and adipsin in a dose dependent manner. The specific mechanism mediating the anti-adipogenesis effects of BRE was the inhibitory effect of BRE on AMP-activated protein kinase activation and the Nrf2/HO-1 pathway. In addition, we found that BRE significantly increased C/EBPβ protein and mRNA, and this was all influenced through Nrf2 activation during an early stage (day 2). BRE inhibits lipid accumulation by regulating adipogenesis and lipogenesis related genes and signaling proteins. BRE may a good candidate for a nutraceutical and pharmaceutical formulation for treating or controlling obesity.

Keywords: black radish, anti-obesity, anti-adipogenic effect, AMPK, Nrf2