In Vitro Antioxidant Activity and Resistance to Ultraviolet Radiation of Polyphenol from Watermelon Rind
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Abstract:
Polyphenols were extracted from watermelon rind using an ultrasound-assisted process. Antioxidant activity of the crude extract was assessed by determining its hydroxyl radical-scavenging activity, 2,2-diphenyl-2-picrylhydrazyl (DPPH)-scavenging activity, ferric-reducing ability of plasma (FRAP) assay, whereas resistance to ultraviolet (UV) radiation was studied using solid Escherichia coli medium. Composition of the polyphenol extract was determined by high-performance liquid chromatography. The results showed that the crude polyphenol extract from watermelon rind exhibited in vitro antioxidant activity and resistance to UV radiation. Additionally, its hydroxyl radical-scavenging activity was weaker than that of Vc, and its DPPH-scavenging activity was equivalent to that of butylated hydroxytoluene (BHT); however, its ferric-reducing activity was significantly stronger than the activity of BHT. When exposed to the same intensity of UV radiation that caused 90% mortality in E. coli, a visibly higher number of surviving E. coli colonies treated with the crude polyphenol extract from watermelon rind was observed than that observed in the control (saline-treated) group. The antioxidant activity and resistance to ultraviolet radiation correlated linearly with the concentration of polyphenol extracted from watermelon rind. The main component of the extract was gallic acid.
