Extraction of Flavonoids from the Flowers of Abelmoschus manihot (L.) Medic by Modified Supercritical CO₂ Extraction and Determination of Antioxidant and Anti-Adipogenic Activity.

Abelmoschus manihot (L.) Medic has been used for many years in Chinese traditional medicine. In this study, supercritical CO₂ plus a modifier was utilized to extract flavonoids from the flowers of Abelmoschus manihot (L.) Medic. The effects of temperature (40 °C-60 °C), pressure (10-30 MPa) and different concentrations of ethanol as modifier (60%-90%, ethanol:water, v/v) on major flavonol content and the antioxidant activity of the extracts were studied by response surface methodology (RSM) using a Box-Behnken design. The flavonol content was calculated as the sum of the concentrations of seven major flavonoids, namely rutin, hyperin, isoquercetin, hibifolin, myricetin, quercetin-3'-O-glucoside and quercetin, which were simultaneously determined by a HPLC method. The antioxidant activity was evaluated by a 2,2-diphenyl-1-picrylhydarzyl (DPPH) free radical-scavenging assay. The results showed that three factors and their interactions could be well fitted to second-order polynomial models (p < 0.05). At the optimal extraction conditions for flavonol content (20 MPa, 52 °C, and 85% ethanol content), the yield of flavonoids was 41.96 mg/g and the IC50 value was 0.288 mg/mL, respectively, suggesting the extract has high antioxidant activity. Furthermore, the anti-adipogenic activity of the extract on the 3T3-L1 cell line was investigated. The results indicated that it can downregulate PPARγ and C/EBPα expression at mRNA. In summary, in this study, we have established a cost-effective method for the extraction of flavonoids from the flowers of Abelmoschus manihot (L.) Medic using supercritical fluid extraction and the extracts exhibited potent antioxidant and anti-adipogenic effects, suggesting a possible therapeutic approach for the prevention and treatment of obesity.