Trace anti-inflammatory β-carboline alkaloid identified in Arenaria kansuensis by two-dimensional chromatography coupled with UniElut C18AEX based solid-phase extraction re-enrichment technology

Abstract

Traditional Chinese medicine is important for discovery of drug precursors. However, information about trace chemical composition of them is very limited due to the lack of appropriate enrichment and chromatographic purification methods In our work, A. kansuensis was taken as an example, a novel two-dimensional reversed-phase/hydrophilic interaction liquid chromatography coupled with UniElut C18AEX solid-phase extraction re-enrichment method based on anti-inflammatory bioactivity-guided assay was developed for gathering and purifying trace β-carboline alkaloids with high purity from the ethyl acetate extract of A. kansuensis. Extraction with ethyl acetate as the first enrichment method, then, a UniElut C18AEX column was employed to re-enrich trace fraction which was hardly detected by diode array detector during high performance liquid chromatography analysis, eighteen grams of UniElut C18AEX was used as sorbent material to pack a 60mL pipette tip for the extraction of β-carboline alkaloids from 100mL of ethyl acetate sample. The whole extraction process was finished in 10min, and the volume of eluent used was only 120mL. The enriching fraction (100mg) was used for the following two-dimensional purification. First-dimensional preparation was carried on a RP-Megress-C18 prep column, and four anti-inflammatory fractions were obtained from the 100mg re-enriching sample with a recovery of 66.9%. A HILIC-XAmide prep column was selected for the second dimensional preparation. Finally, two pair of analogue β-carboline alkaloids and one other β-carboline alkaloid were purified from A. kansuensis. The purity of the isolated compounds was ≫>98%, which indicated that the method was efficient to re-enrich and manufacture single trace β-carboline alkaloids with high purity from A. kansuensis. Additionally, this method showed great potential to serve as a good example for the purification and enrichment of analogue structure anti-inflammation carboline alkaloids from other plant materials.

Keywords: Arenaria kansuensis; Trace re-enrichment; Two-dimensional chromatography; UniElut C18AEX SPE; β-carboline alkaloids.