Optimization of choline chloride-glycerol based natural deep eutectic solvent for extraction bioactive substances from Cinnamomum burmannii barks and Caesalpinia sappan heartwoods

Indonesian cassia (Cinnamomum burmannii Blume) is commonly used as a condiment. It reportedly contains a number of major phytochemical constituents such as trans-cinnamaldehyde and coumarin. Sappan wood (Caesalpinia sappan) is a native plant of Southeast Asia that contains brazilin, a widely known red pigment. This study aimed to determine the optimal extraction conditions using a choline chloride-glycerol (ChCl-glycerol)-based natural deep eutectic solvent (NADES) to obtain greater trans-cinnamaldehyde and brazilin levels from Indonesian cassia and sappan wood. The powders of Indonesian cassia and sappan wood were extracted using ChCl-glycerol-based NADES varied at three different levels: ratio of ChCl to glycerol, ratio of powder to NADES, and the amount of water in NADES. All variables were designed using the Box-Behnken design of response surface methodology to provide 15 extraction conditions. The extraction was performed using ultrasonication-assisted extraction for 30 and 50 min for Indonesian cassia and sappan wood, respectively. Determination of the active compound contents was performed using a high-performance liquid chromatography system equipped with a UV-VIS detector at λmax = 280 nm. The optimization results revealed that the highest levels of trans-cinnamaldehyde, coumarin, and brazilin in NADES extracts were 1907.32, 1735.68, and 368.67 μg/ml, respectively, whereas the lowest levels of these compounds were 453.59, 616.76, and 74.21 μg/ml, respectively. The maximal levels exceeded those obtained using a conventional extraction method, in which 5000 μg/ml Indonesian cassia reflux extract contained only 108.45 μg/ml trans-cinnamaldehyde. Similarly, 1000 μg/ml sappan wood contained only 124.64 μg/ml brazilin. ChCl-glycerol-based NADES was suitable for extracting active compounds from Indonesian cassia and sappan wood; moreover, this solvent is more effective than organic ethanolic coventional solvent.