DL-Tyrosine

Objectives: To evaluate the inhibitory effects of different concentrations of α-methyl-DL-tyrosine on latanoprost-induced iridal hyperpigmentation in rabbits. Methods: We investigated 4 groups of rabbits. Both eyes of the pink, red, and blue groups were treated with latanoprost followed by 0.5%, 1%, and 2% α-methyl-DL-tyrosine (inhibitor) in the right eyes respectively and the green group received only inhibitor. We prospectively investigated the irides, estimated quantitatively total melanin contents, and studied any histopathological changes that occurred. Results: The observers favored hyperpigmentation in the left eyes while in the right eyes they noted a decrease in pigmentation as compared to the baseline. An increase in pigmentation was noted by 93.33% of observers in the left eye of the blue group. A significant difference in the mean melanin contents was noted in the blue group (Right eye = 09.560 μg/g (±0.750), Left eye = 3.730 μg/g (±1.062). There was no evidence of stromal malignant changes, Hemorrhage, mitosis, inflammation, and atypical melanocytes in all specimens. A moderate degree of pigmentation in the left eye of the red group was noted. Mild stromal-free melanin pigment was present in all samples of pink, red and blue groups. Conclusions: The α-methyl-DL-tyrosine significantly inhibited latanoprost-induced iridal pigmentation without causing any histopathological changes at a 2% dose.

The structure of N-triphenylacetyl-L-tyrosine (C29H25NO4, L-TrCOTyr) is characterized by the presence of both donors and acceptors of classical hydrogen bonds. At the same time, the molecule contains a sterically demanding and hydrophobic trityl group capable of participating in π-electron interactions. Due to its large volume, the trityl group may favour the formation of structural voids in the crystals, which can be filled with guest molecules. In this article, we present the crystal structures of a series of N-triphenylacetyl-L-tyrosine solvates with chloroform, namely, L-TrCOTyr·CHCl3 (I) and L-TrCOTyr·1.5CHCl3 (III), and dichloromethane, namely, L-TrCOTyr·CH2Cl2 (II) and L-TrCOTyr·0.1CH2Cl2 (IV). To complement the topic, we also decided to use the racemic amide N-triphenylacetyl-DL-tyrosine (rac-TrCOTyr) and recrystallized it from a mixture of chloroform and dichloromethane. As a result, rac-TrCOTyr·1.5CHCl3 (V) was obtained. In the crystal structures, the amide molecules interact with each other via O-H...O hydrogen bonds. Noticeably, the amide N-H group does not participate in the formation of intermolecular hydrogen bonds. Channels are formed between the TrCOTyr molecules and these are filled with solvent molecules. Additionally, in the crystals of III and V, there are structural voids that are occupied by chloroform molecules. Structure analysis has shown that solvates I and II are isostructural. Upon loss of solvent, the solvates transform into the solvent-free form of TrCOTyr, as confirmed by thermogravimetric analysis, differential scanning calorimetry and powder X-ray diffraction.

The ability of Aspergillus fumigatus L-amino acid oxidase (L-aao) to cause the resolution of racemic mixtures of DL-amino acids was investigated with DL-alanine, DL-phenylalanine, DL-tyrosine, and DL-aspartic acid. A chiral column, Crownpak CR+ was used for the analysis of the amino acids. The enzyme was able to cause the resolution of the three DL-amino acids resulting in the production of optically pure D-alanine (100% resolution), D-phenylalanine (80.2%), and D-tyrosine (84.1%), respectively. The optically pure D-amino acids have many uses and thus can be exploited industrially. This is the first report of the use of A. fumigatus L: -amino acid oxidase for racemic resolution of DL-amino acids.