微波辅助萃取水飞蓟素的动力学机理

Kinetic mechanisms for silymarin by microwave-assisted extraction

为了揭示微波辅助萃取水飞蓟素的动力学机理,该文选择萃取温度(78～130℃)、萃取时间(30～70min)为影响因素,用反应级数、平均表观速率常数和活化能表征物料在萃取过程中动力学行为,对比研究了微波辅助萃取(MAE)和常规的热回流萃取法(RHE)萃取水飞蓟素的过程,并在电子显微镜下分别观察了经2种方法加工后水飞蓟颗粒的微观结构。结果表明:MAE和RHE萃取水飞蓟素的过程均符合一级动力学方程的规律;MAE萃取水飞蓟素的活化能约是RHE的1/5,平均表观速率常数是RHE的48倍。观察水飞蓟颗粒微观结构发现,经MAE萃取后的结构呈现疏松排列的;而经RHE方法萃取后的结构排列紧密。这些结果表明微波的作用使萃取剂和萃取物更容易通过细胞壁,增强了水飞蓟素在基体内的扩散速度,提高了萃取率。

In the paper,extraction temperature(78-130℃)and extraction time(30-70 min)selected as influencing factors,the reaction order,average apparent rate constant and activation energy characterized the kinetic behaviors,a comparative experiment between the microwave-assisted extraction(MAE)and reflux heating extraction(RHE)method was conducted to reveal the kinetic mechanisms for silymarin by microwave-assisted extraction,The micro-structure of milk thistle kernel treated with MAE and RHE,respectively,were observed by scanning microscopy.The result shown that both MAE and RHE method for the silymarin extraction consistent with the regular of first-order kinetics equation, and the activation energy and average apparent rate constant of silymarin during MAE process was nearly 1/5 and 48 times higher than that during RHE process,respectively.The electron microscope image of milk thistle kernel present the loose matrix structure treated by MAE and compact matrix structure treated by RHE.These results reveal that MAE method improves diffusion of both solvent and extracts through cell wall,which enhance the diffusion speed if silymarin inside matrix,and increase the extracts yield.