Abstract: In order to figure out the comprehensive utilization of seed watermelon peel and juice,polyphenols were extracted from the peel of seed watermelon using ultrasonicassisted extraction process,and the composition of the extract was determined by high performance liquid chromatography.The results showed that the optimal extraction conditions were extraction time of 35 min,ethanol concentration of 70 mL/100mL,temperature of 60 ℃,and the ratio of solid to liquid of 1:12.According to the importance of effect on polyphenol extraction yield,factors were ranked to be ratio of solid to liquid > extraction time > temperature > ethanol concentration.The main composition of polyphenols extract was determined to be gallic acid.In addition,the antibacterial acitivity of polyphenol extract was investigated.Apparently,the inhibition zone can be observed on the plate inoculating E.coli with 0.4 mg/mL of polyphenols extracts.The minimal inhibitory concentration of polyphenols extracts was determined to be 0.05 mg/mL.These results suggested that seed melon polyphenols have anti-bacterial application potential.

Key words: peel of seed watermelon, polyphenol, extraction, gallic acid, anti-bacterial activity