Effects of first dimension eluent composition in two-dimensional liquid chromatography

Offline preparative three-dimensional HPLC for systematic and efficient purification of alkaloids from Gelsemium elegans Benth

The natural compound library is the most productive source in drug discovery and alkaloids are the most potential drug leads in natural compounds. Presently, systematic purification of alkaloids remains a substantial challenge. In this study, we developed an offline preparative three-dimensional HPLC (3D-HPLC) method to resolve the problem of systematic purification of alkaloids. Ten Gelsemium standards were used in the construction of the method to evaluate several factors, including column selectivity, column loadability and separation orthogonality. The offline 3D-HPLC method achieved great orthogonal selectivity and resolution power using different stationary phases, mobile phases at different pH, and different mobile phase additives. Application of this 3D-HPLC method to Gelsemium elegans Benth. was evaluated, and 24 indole alkaloids were finally isolated, including four new alkaloids and one first-identified in this plant. Moreover, a total of 229 compounds were estimated to be obtained in this plant, almost twice the number of known Gelsemium alkaloids. Therefore, this 3D-HPLC method will be efficient for systematic purification of alkaloids from Gelsemium elegans Benth. and has the potential for alkaloid preparation from other plants.

The application of on-line two-dimensional liquid chromatography (2DLC) in the chemical analysis of herbal medicines

Herbal medicines are complicated chemical systems containing hundreds of small molecules of various polarities, structural types, and contents. Thus far, the chromatographic separation of herbal extracts is still a big challenge. Two-dimensional liquid chromatography (2DLC) has become an attractive separation tool in the past few years. Particularly, a lot of attention has been paid to on-line 2DLC. In this review, we aim to give an overview on applications of on-line 2DLC in the chemical analysis of herbal medicines since 2010. Firstly, classification and general configurations of on-line 2DLC were briefly introduced. Then, we summarized main applications in herbal medicines of heart-cutting 2DLC (LC-LC), comprehensive 2DLC (LC × LC), and their combinations, with emphasis on LC × LC. Mass spectrometry is the most popular detector coupled with 2DLC, which allows sensitive and accurate structural characterization of herbal compounds. Finally, future developments in on-line 2DLC techniques were also discussed.

Effect of first dimension phase selectivity in online comprehensive two dimensional liquid chromatography (LC×LC)

In this study, we examined the effect of first dimension column selectivity in reversed phase (RP) online comprehensive two dimensional liquid chromatography (LC×LC). The second dimension was always a carbon clad metal oxide reversed phase material. The hydrophobic subtraction model (HSM) and the related phase selective triangles were used to guide the selection of six different RP first dimension columns. Various kinds of samples were investigated and thus two different elution conditions were needed to cause full elution from the first dimension columns. We compared LC×LC chromatograms, contours plots, and fcoverage plots by measuring peak capacities, peak numbers, relative spatial coverage, correlation values, etc. The major finding of this study is that the carbon phase due to its rather different selectivity from other reversed phases is reasonably orthogonal to a variety of common types of bonded reversed phases. Thus quite surprisingly the six different first dimension stationary phases all showed generally similar separation patterns when paired to the second dimension carbon phase. This result greatly simplifies the task of choosing the correct pair of phases for RP×RP.