The effect of extraction method (ultrasonic, maceration, and soxhlet) and solvent type on the extraction rate of phenolic compounds and extraction efficiency of Arctium lappa L. roots and Polygonum aviculare L. grass

The species of Arctium lappa L. roots and Polygonum aviculare L. grass have various therapeutic properties in traditional medicine in East Asian countries. The aim of this study was to investigate the effect of three methods of extracting extracts by ultrasonic bath, maceration, and soxhlet to determine phenolic compounds of Arctium lappa L. roots and Polygonum aviculare L. grass using water and 50% ethanol and the evaluation of extraction efficiency of their extract. The results showed that in the ultrasonic bath extraction method, ethanolic extract of Arctium lappa L. root had the highest content of phenolic compounds (976 mg equivalent to Gallic acid per gram of dry sample), and the highest extraction efficiency in this method was related to Polygonum aviculare L. grass when using both solvents (14%). In the maceration extraction method, the ethanolic extract of Arctium lappa L. root showed the highest content of phenolic compounds (976 mg equivalent to Gallic acid per gram of dry sample), and the highest extraction efficiency in this method was related to the Polygonum aviculare L. grass extracted with water (12%). Also, in the Soxhlet extraction method, ethanolic extract of Arctium lappa L. root showed the highest content of phenolic compounds (578 mg equivalent of gallic acid per gram of dry sample), and the highest extraction efficiency in this method was related to the Polygonum aviculare L. grass extracted with ethanol (18/16%). The content of extraction of bioactive compounds based on the type of solvent, the method, and the type of plant used were significantly different from each other and 50% ethanol solvent was the best solvent for extracting the desired compounds. Arctium lappa L. roots also had the highest phenolic composition and extraction by maceration, soxhlet, and ultrasonic bath methods had the most significant effect on the extraction of phenolic compounds, respectively.