Microwave-assisted method for simultaneous hydrolysis and extraction in obtaining ellagic acid, gallic acid and essential oil from Eucalyptus globulus leaves using Brönsted acidic ionic liquid [HO3S(CH2)4mim]HSO4

Abstract

Brönsted acidic ionic liquid and microwave energy are introduced for catalytic hydrolysis of hydrolysable tannins into ellagic acid and gallic acid and simultaneous extraction bioactive substances in the present study. Brönsted acidic ionic liquid-based microwave-assisted simultaneous hydrolysis and extraction (BMSHE) method was employed in obtaining ellagic acid, gallic acid and essential oil from Eucalyptus globulus leaves. [HO3S(CH2)4mim]HSO4 was used as a dual hydrolysis catalyst and extraction solvent in the proposal approach. The optimized parameters were obtained as follows: [HO3S(CH2)4mim]HSO4 concentration of 1.0M, liquid–solid ratio of 30mL/g, microwave irradiation time of 20min and microwave irradiation power of 385W. Yields of ellagic acid, gallic acid and essential oil under these conditions are 3.32±0.08mg/g, 3.83±0.11mg/g and 4.82±0.18mg/g, respectively. Compared with the reference solvent, [HO3S(CH2)4mim]HSO4 shows excellent solvent effect and catalytic activity. Comparison between BMSHE and hydrodistillation indicated the proposed approach is a high efficient, time-saving, low energy consumption and eco-benign methodology. Method validation studies also evidenced that BMSHE is credible for the preparation of ellagic acid and gallic acid. It is reasonable to assume that this method would become a new potential candidate for the preparation of some other kinds of bioactive substances from plant materials.