绿茶、桑叶和臭黄荆叶细粉水提液抑菌和抗氧化能力

探究绿茶、桑叶和臭黄荆叶3种植物干叶细粉水提液的抑菌和抗氧化能力。采用当量法测定3种原料中黄酮、多酚含量,二倍稀释法测定水提液对大肠杆菌、金黄色葡萄球菌的最小抑菌浓度和最小杀菌浓度,牛津杯法分析原料的抑菌活性。利用分光光度法研究3种水提液及其两两等比混合后的DPPH自由基清除率、羟自由基清除率和Fe2+螯合能力。结果表明,绿茶粉中水溶性黄酮、多酚含量最高,分别为62.22、133.82 mg/g,桑叶粉次之,臭黄荆叶粉最少。绿茶、桑叶和臭黄荆叶细粉在DPPH自由基清除率、羟自由基清除率和Fe2+螯合能力方面无协同作用,但黄酮、多酚含量与其抑菌和抗氧化活性间存在显著的量效关系(P<0.05)。因此,绿茶、桑叶和臭黄荆叶细粉水提液抑菌和抗氧化能力依次减弱,且三者抗氧化活性没有协同增效作用。

Study on antioxidant and antibacterial ability of water extracts from the powder of green tea,mulberry leaves and premna leaves

The purpose of this study is to investigate the antibacterial and antioxidant capacity of green tea,mulberry leaves and premna leaves.The content of flavonoids and polyphenols in three raw materials was determined by equivalent method.Determination of minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC)of water extracts against Escherichia coli and Staphylococcus aureus by two-fold dilution method.Analysis of antibacterial activity of raw materials on two kinds of Bacteria by Oxford Cup Method.The DPPH free radical scavenging power,hydroxyl scavenging power and Fe2+chelation ability of the three aqueous extracts and their ratios were studied by spectrophotometry.The results showed that the content of water-soluble flavonoids and polyphenols in green tea powder was the highest,which were 62.22 mg/g and 133.82 mg/g,respectively,followed by mulberry leaf powder and premna leaf powder.There was no synergistic effect between green tea powder,mulberry leaf powder and premna leaf powder on DPPH free radical scavenging power,hydroxyl scavenging power and Fe2+chelation ability.However,there is a significant dose-effect relationship between the content of flavonoids and polyphenols in the raw materials and their antibacterial and antioxidant activities(P<0.05).Overall,the antibacterial and antioxidant capacity of the aqueous extracts of green tea,mulberry leaves and premna leaves were weakened in turn,and the antioxidant activities of the three had no synergistic effect.