利用微波辅助法提取多酚。结果表明,微波功率、提取时间、料液比的增加显著提高多酚提取率。微波辅助法提取牛蒡叶多酚的较佳条件为:提取时间3min,微波功率160W,料液比1g:20mL,提取2次。在此条件下,多酚提取率平均值为93.93%。DPPH自由基试验、羟自由基清除能力试验结果表明,牛蒡叶提取物具有较强的抗氧化活性,牛蒡叶提取物浓度为0.90mg/mL时,提取物对DPPH自由基的清除率为51.73%。抑菌试验结果表明,牛蒡叶微波提取物对革兰氏阳性菌与阴性菌都具有很强的抗菌活性,对金黄色葡萄球菌、大肠杆菌、志贺氏菌的最低抑菌浓度(MIC)分别为2.20,2.80,3.00mg/mL。

Microwave technique was employed to extract phenols from burdock leaves.The effects of four independent variables(time,microwave power,extraction times,and solvent to solid ratio) on the recovery of phenols from burdock leaves were evaluated.The good conditions for microwave extraction of phenols were determined.The optimal conditions to obtain the highest recovery of phenols were:three minutes of extracting time,160W of microwave power,extraction twice and 20 mL/g of solvent to solid ratio.Under these optimal conditions,the average recovery of phenols was 93.93%.The experiments indicated that the antioxidant activity(DPPH radical scavenging ability,hydroxyl radical scavenging capability) of the extract from burdock leaves was very high.Moreover,the extract of burdock leaves exhibited higher antibacterial activity.The MIC values of burdock leaves extract against Staphylococcus aureus,Escherichia coli and Shigella dysenteriae were determined to be 2.20,2.80 and 3.00 mg/mL.