Microwave and ultrasonic effects on the extraction and antioxidation of larch bark polyphenols.

We studied microwave and ultrasonic effects on the extraction, chemical structure and antioxidation properties of pine polyphenols in the bark of larch trees. The results show that using a 50% ethanol solution as solvent increases the extraction of polyphenols from the bark by microwave treatment by 6.76% and by ultrasonic treatment by 14.73%. From observations with a scanning electron microscope we found pore sizes in the surface microstructure of the larch bark residues ranging between 1.5-2.5 μm in the solvent, between 7-13 μm by microwave and 17-26 μm by ultrasonic treatments. An infrared spectrum analysis showed that the chemical structures of pine polyphenols from the three extraction methods did not changed significantly. The antioxidation experiments revealed that the total reduction power and capacity of DPPH free radical scavenging of pine polyphenols did not significantly change among the three extraction methods (P0.05).