Determination of coumarins in Fructus cnidii by using deep eutectic solvent elution-based carboxymethyl chitosan matrix solid-phase dispersive extraction

Fructus cnidii has been used as a folk medicine for thousands of years. Coumarins are the active compounds behind its therapeutic effect. Thus, the determination of coumarins is necessary for quality evaluation of Fructus cnidii. However, most traditional methods for determining coumarins in natural products are time-consuming, organic solvent-consuming, and are not amenable to the analysis of volatile compounds. Herein, a novel method termed deep eutectic solvent-based carboxymethyl chitosan matrix solid-phase dispersion extraction was proposed and applied to the determination of coumarins in Fructus cnidii, including bergapten, imperatorin, and osthole. For the first time, carboxymethyl chitosan was applied as a dispersant and hexanoic acid-monoethanolamine (a deep eutectic solvent) was used as an eluting solution in the analytical procedure. The deep eutectic solvent dissolved the dispersant (CMC), thereby releasing the analytes and precluding irreversible adsorption. The analytes could be simultaneously concentrated during the elution process. The newly developed method was coupled with HPLC for the determination of coumarins in Fructus cnidii. Several critical parameters affecting the extraction performance, including the molar ratio of the sample to dispersant, grinding time, type of eluting solution, and amount of acid added were investigated. The method was validated by using HPLC. The good linearity (r ≥ 0.9998), a low detection limit, satisfactory precision (intra-day precision is less than 1.88 %, inter-day precision is less than 6.71 %) and accuracy (recovery is 91.3 %-95.0 %) were obtained. Under the optimal conditions, the proposed method had advantages including a simpler extraction process, smaller sample amount (10 mg), less organic reagent (2.4 mL), shorter extraction time (7 min), and no additional concentration process. It is also allowed the analysis of volatile compounds and is environment friendly.