Quantification of amino acids secreted by yeast cells by hydrophilic interaction liquid chromatography-tandem mass spectrometry.

Monitoring the levels of amino acids (AAs) in biological cell cultures provides key information to understand the regulation of cell growth and metabolism. Saccharomyces cerevisiae can naturally excrete AAs, making accurate detection and determination of amino acid levels within the cultivation medium pivotal for gaining insights into this still poorly known process. Given that most AAs lack ultraviolet (UV) chromophores or fluorophores necessary for UV and fluorescence detection, derivatization is commonly utilized to enhance amino acid detectability via UV absorption. Unfortunately, this can lead to drawbacks such as derivative instability, labor intensiveness, and poor reproducibility. Hence, this study aimed to develop an accurate and stable hydrophilic interaction liquid chromatography-tandem mass spectrometry analytical method for the separation of all 20 AAs within a short 17-min run time. The method provides satisfactory linearity and sensitivity for all analytes. The method has been validated for intra- and inter-day precision, accuracy, recovery, matrix effect, and stability. It has been successfully applied to quantify 20 AAs in samples of yeast cultivation medium. This endeavor seeks to enhance our comprehension of amino acid profiles in the context of cell growth and metabolism within yeast cultivation media.

Overview of chromatographic and electrophoretic methods for the determination of branched-chain amino acids.

The significance of branched-chain amino acids in diseases was clearly shown over the years. This review aims to describe the available techniques for their analytical determination. The article provides examples of the use of various analytical methods. The methods are divided into two categories: derivatization and non-derivatization approaches. Separation is achieved through different chromatography or capillary electrophoresis techniques and can be combined with different detectors such as flame ionization, ultraviolet, fluorescence, and mass spectrometry. It compares the application of various derivatization reagents or detection as such for different detectors.

In vitro evaluation of intestinal absorption of tiliroside from Edgeworthia gardneri (Wall.) Meisn.

Although Edgeworthia gardneri (Wall.) Meisn and its main component tiliroside (TIL) show good bioactivity, its intestinal absorption data supporting its low bioavailability have not been reported.The evaluation results of three absorption models in vitro and in vivo indicated that the results of the Ussing chamber model were basically consistent with the results of in vivo experiments. It was thus applied to investigate the characteristics of TIL across various intestinal regions and the interaction between TIL and adenosine triphosphate (ATP)-binding cassette family proteins (ABC) including, P-glycoprotein (P-gp), multidrug resistance-associated protein 2 (MRP2), and breast cancer resistance protein (BCRP).The data of the bi-directional transport showed that the ileum had the higher apparent permeability coefficient (Papp) of TIL than duodenum and jejunum, suggesting the best absorption of TIL in the ileum.In the presence of the MRP2 inhibitor, the absorption of TIL from water extracts of E. gardneri (Wall.) Meisn (WAE) was improved, indicating that MRP2 other than P-gp and BCRP affected the absorption of TIL and might be responsible for its low bioavailability. This study laid the foundation for enhancing the bioavailability of TIL and highlighted the influences of efflux transporters on bioavailability.

Development of Ussing model coupled with artificial membrane for predicting intestinal absorption mechanisms of drugs.

The absorption mechanisms of drugs play an important role on development and various application of drugs. However, the present methods of absorption mechanisms are not perfect enough. Hence, exploring a novel method to accurately predict the absorption mechanisms is necessary. In this study, we developed an Ussing model coupled with artificial membrane (AM-Ussing) for predicting the permeability of passive diffusion. Furthermore, by the combination of AM-Ussing and Ussing model, the three different mechanisms including efflux transport, uptake transport and passive diffusion could be successfully distinguished. Specifically, 12 drugs of passive transport were selected to evaluate AM-Ussing. And the high permeability correlation between AM-Ussing model and traditional Ussing model indicated that AM-Ussing was successfully established. Moreover, the absorption mechanisms of 11 drugs were predicted by the combination of AM-Ussing and Ussing model. The results showed that three kinds of absorption mechanisms mentioned can be predicted successfully. Therefore, AM-Ussing model is a potential tool to assess passive diffusion, and the combined use of AM-Ussing and Ussing model is an effective method to predict the intestinal absorption mechanisms of drugs.