籽瓜皮多酚的体外抗氧化及抗紫外线辐射作用研究

利用超声波辅助提取籽瓜皮中的多酚类物质,采用总铁还原能力(FRAP)、清除1,1-二苯基-2-苦肼基自由基(DPPH·)的能力、清除羟自由基的方法测定籽瓜皮粗提物的抗氧化性,并利用大肠杆菌固体培养基培养法观察其抗紫外线辐射作用。以高效液相色谱法对多酚萃取物的主要成分进行测定。结果表明,籽瓜皮多酚粗提物具有一定的体外抗氧化能力及抗紫外线辐射能力。其清除羟自由基的能力稍弱于Vc,清除DPPH自由基能力与2,6-二叔丁基对甲酚(BHT)相当,但其铁还原能力远比BHT强。给与使大肠杆菌致死率达到90%以上的辐射强度,与生理盐水相比,籽瓜皮多酚粗提物能提高大肠杆菌存活率。籽瓜皮多酚的抗氧化性及抗紫外线辐射的作用与其浓度都呈现出一定的线性相关性。籽瓜皮多酚的主要成分为没食子酸。

In Vitro Antioxidant Activity and Resistance to Ultraviolet Radiation of Polyphenol from Watermelon Rind

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.