Abstract
Ionic liquid based, microwave-assisted extraction (ILMAE) was successfully applied to the extraction of proanthocyanidins from Larix gmelini bark. In this work, in order to evaluate the performance of ionic liquids in the microwave-assisted extraction process, a series of 1-alkyl-3-methylimidazolium ionic liquids with different cations and anions were evaluated for extraction yield, and 1-butyl-3-methylimidazolium bromide was selected as the optimal solvent. In addition, the ILMAE procedure for the proanthocyanidins was optimized and compared with other conventional extraction techniques. Under the optimized conditions, satisfactory extraction yield of the proanthocyanidins was obtained. Relative to other methods, the proposed approach provided higher extraction yield and lower energy consumption. The Larix gmelini bark samples before and after extraction were analyzed by Thermal gravimetric analysis, Fourier-transform infrared spectroscopy and characterized by scanning electron microscopy. The results showed that the ILMAE method is a simple and efficient technique for sample preparation.
Highlights
Larix gmelini is a deciduous tree primarily distributed in northeast China, north Sakhalin and eastSiberia
The structure of ionic liquids has a significant influence on their physicochemical properties, which might greatly affect the extraction yield of target analytes [19]
The results showed that the ionic liquids based on
Summary
Larix gmelini is a deciduous tree primarily distributed in northeast China, north Sakhalin and east. Proanthocyanidins have been found in large quantities in L. gmelini bark and have been recognized as a multipurpose natural component with great economic potential and environmental value, attracting increasing attention [2,3,4,5]. Proanthocyanidins, known as condensed tannins, are mainly procyanidins with (+)-catechin and (−)-epicatechin as constitutive units They are naturally occurring polymeric phenolic compounds that are widely found in various fruits, vegetables, seeds, flowers and bark. It is of interest to investigate the microwave-assisted extraction of proanthocyanidins using ionic liquids. The potentiality of ionic liquids as alternative solvents in the MAE of proanthocyanidins from L. gmelini bark was investigated, and the results compared with conventional extraction methods. The microstructures and chemical structures of L. gmelini bark samples before and after extraction were investigated by Thermal gravimetric analysis (TG), Fourier-transform infrared spectroscopy (FTIR) and characterized by scanning electron microscopy (SEM)
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