Extraction efficiency of loganic acid and gentiopicroside from Gentianae radix et rhizoma by deep eutectic solvent-based ultrasound-assisted extraction

This study describes the extraction efficiency of loganic acid and gentiopicroside from Gentianae radix et rhizoma using the deep eutectic solvent-based ultrasound-assisted extraction (DES-UAE) method. A comparison was made against 12 deep eutectic solvents (DESs) as alternative extraction solutions. The extraction efficiency of DES-4 (prepared from choline chloride and lactic acid) exceeded that of other DESs. A single factor experiment and response surface methodology (RSM) were adopted, and the optimal processing parameters of DES-UAE were: the water content of DES-4 was 19.9 %, solid/liquid was 29.3 mg/ml, extraction temperature was 50.8 °C and extraction time was 26.8 min. Under these conditions, the extraction efficiency of loganic acid and gentiopicroside was 7.6986 mg/100 g. The results of scanning electron microscopy (SEM) indicated that the unextracted powder exhibited a granular shape with rough surface and complete structure. Moreover, the ultrasonic extraction of Gentianae radix et rhizoma powder with DES-4 as extraction solution caused significant damage to the surface structure of the powder, creating numerous fine pores on the surface. This suggested that DES-4 had higher permeability and erosive force, which effectively destroyed the cell wall.