Microwave-Assisted Extraction of Flavonoids from Pine Needle and Identification of (–)-Epicatechin

Microwave-assisted extraction was applied for preparation of flavonoids from pine needle in this work. During treatment, microwave interacted well with solvent molecules. The pressure was built up inside the cell, improving the porosity of the plant matrix, which allowed better penetration of flavonoids. A regression mathematical model was constructed by response surface methodology to evaluate the effects of three independent variables (ethanol concentration, time and temperature) on the yield of flavonoids. These factors apparently affected the dissolution of flavonoids from pine needle tissues under microwave conditions. By determination of P-value and R-2, the fitness of this model was confirmed to be significant. The optimal conditions to extract flavonoids were 25.2%, 70 degrees C and 8 min. A flavonoid was purified by column chromatography and was identified to be (-)-epicatechin by nuclear magnetic resonance spectroscopy and mass spectrometry. Both (-)-epicatechin and flavonoids extract of pine needle showed good radical scavenging activities against DPPH and superoxide anion radicals, which were better than butylated hydroxyanisole.