Deep eutectic solvent-based extraction coupled with green two-dimensional HPLC-DAD-ESI-MS/MS for the determination of anthocyanins from Lycium ruthenicum Murr. fruit

Abstract

This study aimed to extract and separate total anthocyanins from Lycium ruthenicum Murr. by combining deep eutectic solvents (DES) with macroporous resin chromatography and to develop green analytical methods for the determination of anthocyanins. Choline chloride/1,2-propanediol (1 : 2, mol mol⁻¹) containing 10% water (v/v) was screened as the optimal extraction solvent, and extraction at 52 °C for 45 min using a liquid/solid ratio of 20 : 1 gave the maximum extraction yield of total anthocyanins (4.45 ± 0.07 mg g⁻¹). According to the static/dynamic adsorption and desorption tests, LS-32 macroporous resin has the ability to separate anthocyanins from DES with a recovery ratio above 95%. An off-line heart-cutting two-dimensional HPLC-DAD/ESI-MS method was developed for the qualitative and quantitative analysis of L. ruthenicum anthocyanins using environmentally friendly mobile phases. Ethanol and a tartaric acid solution (0.3 mol L⁻¹) were used as the mobile phases of the first-dimensional HPLC-DAD method, and 15 anthocyanin peaks were detected within 17 min. The second-dimensional HPLC-MS method was used to identify the main anthocyanin peaks in the first dimension. Method validation showed that the developed method was accurate, stable and reliable for the analysis of L. ruthenicum anthocyanins. The present study provides an excellent alternative green method for the preparation and determination of anthocyanins from plant material.