pyrrolidine-2-carboxylic acid

(R)-pyrrolidine-2-carboxylic acid (D-Proline) is an isomer of the naturally occurring amino acid L-Proline. D-amino acids, including D-Proline, are found in relatively high abundance in human plasma and saliva, potentially originating from bacterial sources or endogenous production via amino acid racemase activity.

(R)-5-Oxopyrrolidine-2-carboxylic acid (D-Pyroglutamic acid) is a cyclic derivative of glutamic acid, physiologically present in mammalian tissues. It releases GABA from the cerebral cortex and exhibits anti-anxiety effects in a simple approach-avoidance conflict situation in rats. In clinical pharmacology experiments, it significantly shortens the plasma half-life of ethanol during acute intoxication.

4-Hydroxypyrrolidine-2-carboxylic acid (4-hydroxyproline) is a non-protein amino acid and endogenous metabolite present in collagen that modulates collagen elasticity and can be used as a diagnostic marker for bone conversion and liver fibrosis.