Application of natural deep eutectic solvents for extraction and determination of phenolics in Cajanus cajan leaves by ultra performance liquid chromatography

In this study, novel and green natural deep eutectic solvents (NADESs) as extraction media, are presented for the extraction and determination of phenolics in Cajanus cajan leaves by ultra performance liquid chromatography. Fourteen different NADES systems were investigated for the extraction of phenolics with diverse polarity in C. cajan leaves. Experiments with different extraction solvents and multivariate data analysis demonstrated that the NADES composed of choline chloride and maltose possessed excellent extractability for both polar and weak polar compounds compared to conventional solvents. The influential parameters of microwave-assisted extraction procedure with NADES were examined and optimized. The optimized conditions were as follows: extraction solvent 20% of water in choline chloride/maltose (1/2), extraction temperature 60   °C, liquid/solid ratio 30:1   mL/g and irradiation time 12   min. Moreover, a fast and sensitive UPLC method was firstly developed for the comprehensive analysis of fourteen phenolics in C. cajan leaves. This method was performed within 40   min, and exhibited satisfactory linearity, precision and recovery. These results indicate that the proposed method represents an excellent alternative for the extraction and quantification of phenolics in plant materials.