Synthesis and characterization of natural deep eutectic solvents as green extractants for isolation of bioactive flavonoids from Amaranthus viridis

The application of principles of Green Chemistry is gaining importance in various fields of research to eliminate the risk of environmental pollution from toxic chemicals. Safer industrial processes reduce the risk of health problems to the consumers as well as result in a sustainable and cleaner environment. This paper indicated the synthesis of sustainable green solvents having greater solvation property to extract phytochemicals from plants in comparison to an organic solvent. Natural deep eutectic solvents (NADES) containing choline chloride (ChCl), 1,2-propanediol (PG) and citric acid (CA) were prepared followed by the study of its physicochemical properties. Selected NADES's were then used for the first time to extract bioactive components from Amaranthus viridis (AV) and compared with the ethanolic extract. The results indicated the total phenolic content (TPC) value of 54.6, 250, 40.6 mgGAE/g, total flavonoid content value (TFC) of 16.5, 82.1, 20.4 mgQUE/g and antioxidant activity of 30.3, 42.9, 22.6 mg/ml of AV extract in ChCl:PG:H2O-1:2:1 (AV-PG), AV extract in ChCl:CA:H2O-1:1:1 (AV-CA) and AV extract in ethanol (AV-E) respectively. A high concentration of bioactive components in NADES extracts was confirmed by phytochemical analysis comparing to ethanol extract. Antibacterial activity of AV-CA extract showed inhibition zone of 30 mm against both gram-positive and gram-negative bacterial strains. From the results it can be concluded that NADES extracts can be used for biomedical applications as an improvement in the drug delivery system by eliminating the toxic solvents.