Kinetic Mechanisms for Preparing Silymarin via Microwave-assisted Extraction

The kinetic mechanism for the preparation of silymarin from milk thistle seeds was studied during the microwave-assisted extraction (MAE) process. The results showed that the transfer rate of silymarin from milk thistle seeds increased with the microwave output power and temperature during MAE processing. The apparent extraction rate constant k (s-1) was 1.2028×10-2 , 1.2248×10-2 , and 1.2485×10-2 , and diffusion coefficient D (m2·s-1 ) was 4.21×10-10, 4.29×10-10 , and 4.37×10-10 at the microwave temperatures of 383, 393, and 403 K, respectively, in the silymarin MAE process. With the help of scanning electron microscopy (SEM), the microstructures of the samples extracted by MAE were observed. The results revealed that the increased efficiency and rate of MAE of silymarin could be attributed mainly to the subsequent cell change resulting from superheating effects during MAE.