Optimized conditions for extraction, quantification and detection of bioactive compound from Nettle (Urtica dioica L.) using the deep eutectic solvents, ultra-sonication and liquid chromatography-mass spectrometry (LC-DAD-ESI-MS/MS)

The bioactive constituents of Nettle (Urtica dioica L.) plants were extracted by green and environmentally friendly methods using several deep eutectic solvents (DESs) followed by liquid chromatography-mass spectrometry separation and identification. To optimize the extraction process, bio-solvents composed of organic acids such as hydrogen bond donors (HBD) and mannitol/menthol/sugars as HBA were selected and coupled with ultrasound-assisted extraction. The maximum bioactive compound contents were TPC 2423 mg GAE/100 g, TFC 134.71 mg CE/100 g, and DPPH 1071.05 mol TE/mL. The optimum extraction parameters to achieve the highest values of phenolic compounds from Nettle (Urtica dioica L.) via UAE-DES were obtained at an extraction temperature 70 & DEG;C, extraction time of 30 min, and water addition on DES 20%. The ideal experimental conditions were confirmed using the Central Composite Design (CCD) of the Response Surface Methodology (RSM) model to analyze the significance of extraction parameters demonstrating high prediction levels of the bioactive compounds. Liquid chromatography coupled with diode array detection and electrospray ionization tandem mass spectrometry (LC-DAD-ESI-MS/MS) was used to identify the extracts. The results showed that quercetin-3-O-rutinoside, 5-ocaffeoylquinic acid, and caffeoyl malic acid were the three compounds with the highest abundance. For the first time, the extraction of bioactive compounds from nettle using a food-grade DES that contains GRAS components is reported. According to these findings, the best solvent for extracting bioactive substances for food-grade applications is DESCAMAL (citric acid/maltose).