Comparing DES-mediated ultrasound- and heat-assisted extraction of bioactive metabolites from Saussurea lappa and optimization by RSM and validation studies

Abstract

Saussurea lappa roots have several important uses in traditional medicine. An efficient and sustainable process is needed to obtain bioactive compounds from them. To address this industrial need, the current project was designed with the objective of developing a green and effective method for the extraction of bioactive metabolites from Saussurea lappa roots. Glycerol-choline chloride DES (deep eutectic solvent) diluted (50 %) with water was used as an extractant and two techniques HAE (heat-assisted extraction) and UAE (ultrasound-assisted extraction) were optimized through 3-factors Box-Behnken designs of RSM (response surface methodology). For each technique, four dependent factors were selected that were total polyphenols (TP, gallic acid equivalents/g (GAE/g)), total flavonoids (TF, rutin equivalents/g (RE/g)), antioxidant capacity (AC, %), and metal chelating capacity (MCC, %). Under the optimized conditions, TP, TF, AC, and MCC in UAE were 7.51 mg GAE/g DM, 4.87 mg RE/g DM, 60.14 % and 62.13 %, respectively, with % error 0.92–4.13, while in HAE, they were 3.48 mg GAE/g DM, 4.40 mg RE/g DM, 51.46 % and 55.61 %, respectively with % error 0.22–4.56. The models were strongly supported by validation experiments. Thus, UAE was more efficient and sustainable than HAE and can, therefore, effectively be used for the extraction of bioactive molecules from S. lappa roots on an industrial scale.