Separation of vigabatrin enantiomers using mixed-mode chromatography and its application to determine the vigabatrin enantiomer levels in rat plasma

Use of Commercial Mixed-Mode Stationary Phases and Sorbents in the High-Performance Liquid Chromatography Analysis and Solid-Phase Extraction of Ionized and Hydrophilic Bioactive Compounds

Mixed-mode high-performance liquid chromatography (HPLC) is increasingly used for the analysis of ionic and highly hydrophilic drugs, which are difficult to separate by conventional single-mode HPLC. In the former case, chromatographic separation is achieved using one of the several commercially available mixed-mode stationary phases, typically combinations of reversed and ion-exchange phases. Moreover, mixed-mode stationary phases can be used as solid-phase extraction (SPE) sorbents. This review focuses on the recent applications of mixed-mode stationary phases in the chromatographic analysis of bioactive compounds, such as drugs, herbicides, and pesticides. Specifically, we briefly summarize HPLC methods utilizing mixed-mode stationary phases and SPE pretreatment procedures utilizing mixed-mode sorbents developed in the last decade, thus providing a reference work for overcoming the difficulties in analyzing ionized or hydrophilic drugs by conventional reversed-phase chromatography.

Determination of d- and l-Amino Acids in Garlic Foodstuffs by Liquid Chromatography-Tandem Mass Spectrometry

Black garlic is currently attracting interest as a health food and constituent of commercial supplements; however, no data regarding the d-amino acids within black garlic have been reported. Therefore, the amino acid compositions of methanol extracts from fresh and black garlic were compared herein. We investigated the contents of the d- and l-forms of amino acids in commercial fresh, black, and freeze-dried garlic foodstuffs by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using a pre-column chiral derivatization reagent, succinimidyl 2-(3-((benzyloxy)carbonyl)-1-methyl-5-oxoimidazolidin-4-yl) acetate. Several d-amino acids, namely, the d-forms of Asn, Ala, Ser, Thr, Glu, Asp, Pro, Arg, Phe, Orn, Lys, and Tyr, were observed in the methanol extract of black garlic, whereas only d-Ala was detected in that of fresh garlic foodstuffs. These data suggest that several d-amino acids can be produced during fermentation for preparing black garlic.