Abstract: Aim: To optimize the extraction of total flavonoids from pumpkin seedlings and to evaluate their free radical scavenging activity. Methods: Aqueous ethanol solution was the solvent for flavonoid compounds in pumpkin seedlings. Orthogonal array design method was employed for the optimization of extraction process. Free radical scavenging activity evaluation was achieved by determining the abilities to scavenge DPPH and hydroxyl free radicals (by salicylic acid method). Results: The optimized extraction conditions were found to be extraction at 70 ℃ for 4 h using 85% aqueous ethanol solution at a solid/liquid ratio of 1:25 (g/mL). The extraction efficiency for total flavonoids from pumpkin seedlings reached up to 2.56% under these conditions. The median effective concentration (EC50) of total flavonoids from pumpkin seedlings against DPPH and hydroxyl free radicals were determined to be 0.017 mg/mL and 0.019 mg/mL, respectively. Conclusion: Flavonoid compounds are abundant in pumpkin seedlings and those from pumpkin seedlings have strong free radical scavenging activity.

Key words: pumpkin sprout, total flavonoids, extraction, antioxidant activity