DES-based microwave- and ultrasound-assisted extraction of natural products from Rumex hastatus as per response surface methodology

Abstract

Rumex hastatus D. Don is a medicinal wild herb that abundantly grows in many parts of the world. The current work explores the extraction of its polyphenolic and antioxidant compounds using glycerol-choline chloride deep eutectic solvent and two modern techniques, ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE). The optimization was done as per the response surface methodology. Six responses were studied including total phenolic content (TPC), total flavonoid content (TFC), total condensed tannin content (TCT), ferrous iron-chelating (FIC) activity, DPPH radical scavenging activity (RSA), and ferric reducing antioxidant potential (FRAP). The optimal factors for MAE were 10 s extraction time, 229.40 W power, 40 mL/g SSR (solvent-to-solid ratio) and 60 % DES concentration with the predicted TPC, TFC, TCT, FIC, RSA and FRAP as 64.46 mg GAE/g PM, 155.78 mg RE/g PM, 129.73 mg CE/g PM, 51.46 mg EDTAE/g PM, 235.84 mg AAE/g PM and 129.14 mg AAE/g PM, respectively. For UAE, the predicted optimal factors were 24.30 min sonication time, 47 °C extraction temperature, 40 mL/g SSR and 60 % DES concentration with the predicted TPC, TFC, TCT, FIA, RSA, and FRAP as 56.54 mg GAE/g PM, 148.24 mg RE/g PM, 155.60 mg CE/g PM, 57.83 mg EDTAE/g PM, 240.56 mg AAE/g PM and 111.71 mg AAE/g PM, respectively. Both the models were strongly supported by the validation study with minimal % errors; 2.53–6.38 % for MAE and 1.14–5.30 % for UAE. MAE was more efficient than UAE in terms of time input and recovery of total polyphenols. Therefore, the method based on DES-MAE can safely be recommended for use on an industrial level for obtaining bioactives from R. hastatus.