Detection of amino acids and their enantiomeric ratios in various samples, and the development of a new stationary phase for the chiral separation of amino acids.

摘要

The study of amino acids is very important in the food industry, pharmaceutical industry, and the medical field. Over the past twenty years, studies have found higher than expected levels of D-amino acids in foods and beverages. Despite the fact that several studies have reported the concentrations of various free amino acids in tobacco, their enantiomeric composition is unknown. Both the absolute and enantiomeric compositions of proline, alanine, asparagine, aspartic acid, valine, methionine, leucine, and phenylalanine were determined for three strains of tobacco leaf, three types of smokeless tobacco, and six different blended filtered and non-filtered reference cigarettes. Some of the highest levels of D-amino acids ever found in agricultural products were observed. Possible mechanisms for the production of these D-amino acids are considered. The relevance of D-amino acids in tobacco is discussed.; Many chiral thiols such as cysteine, homocysteine, N-acetylcysteine (NAC), and penicillamine are biologically important compounds. Among other roles, they act as antioxidants, therapeutic agents, and indicators of disease. Like other amino acids in biological samples, they are usually derivatized to enhance sensitivity in detection. But most derivatizing agents react with the amine group. Selectively derivatizing only the thiol moiety with a fluorescent group eliminates the large number of amine containing background compounds that are present in biological samples. Most of these thiol specific derivatizing agents require complex and lengthy reactions and produce unstable derivatives. And there have been few reports on the enantiomeric resolution of thiol containing amino acids which have been fluorescently tagged exclusively through the sulfhydryl group. The first HPLC enantioresolution of N(1-pyrenyl)maleimide (NPM) and ThioGlo(TM)3 derivatized compounds is reported on teicoplanin and naphthylethyl-carbamate-beta-cylclodextrin (NEC-beta-CD) chiral stationary phases.; Macrocyclic antibiotics have proven to be very selective and widely applicable chiral stationary phases (CSPs). The teicoplanin CSP has produced some of the best separations for amino acids as well as other types of compounds. Two similar CSPs are produced and compared to the teicoplanin CSP. The first is an aglycone of teicoplanin produced by removing the three carbohydrate moieties from tiecoplanin. This CSP proved to be highly selective for amino acids and provided insight into the role of these sugar units for the antibiotic. The second CSP is made from another macrocyclic antibiotic, A-40,926 which is structurally very similar to teicoplanin. This CSP did not prove to be superior to the teicoplanin CSP for any specific class of compounds, but did prove to be more retentive and provide higher resolution for many compounds.