Extraction of glabridin and total flavonoids from Glycyrrhiza glabra L.residues using deep eutectic solvents and its pretreatment effect
Radix glycyrrhizae was a commonly used herbal drug in traditional Chinese medicine;however,the raw material utilization ratio was often low.Glycyrrhiza glabra L.residues rich in glabridin were used as raw materials for extracting glabridin and total flavonoids using deep eutectic solvents(DES)in this study.This study revealed that the optimum extraction conditions were a mole ratio of choline chloride to propanoic acid of 1∶4,10％water in DES,a liquid-to-solid ratio of 30∶1(Vim,mL/g),a temperature of 80 ℃,and an extraction time of 60 min.With these conditions,the study achieved a glabridin yield of 0.58 mg/g and a total flavonoid yield of 29.68 mg/g.After DES extraction,over 60％of the lignin and hemicellulose in G.glabra L.residues were removed,while over 80％of the cellulose was retained.After DES extraction,cellulose became more accessible,and its degree of polymerization decreased.X-ray diffraction analysis revealed an increase in the size and surface area of the cellulose crystals.Scanning electron microscopy demonstrated visible pores and cracks on the surface,and the biomass appeared translucent.These changes had a significant impact on the enzymatic digestion efficiency of G.glabra residues after extraction.Consequently,this study demonstrated that microwave-assisted deep eutectic solvent extraction simultaneously had a pretreatment effect on the G.glabra residue,which created a basis for subsequent cellulose utilization.
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