title: Pharmacokinetics of theanine enantiomers in rats.
abstract: Theanine, first discovered in tea, is a chiral nonproteinic amino acid that has been reported to have cardiovascular, neurological, and oncological effects. It is being considered as a therapeutic/medicinal agent and additive in consumer products. The present study evaluated the pharmacokinetics of D-theanine, L-theanine, and D,L-theanine in plasma and urine using LC-ESI/MS in rats after oral (p.o.) and intraperitoneal (i.p.) administration. Oral administration data indicated that gut absorption of d-theanine was far less than that of L-theanine. However, after i.p. administration, plasma theanine concentrations of L- and D-theanine were similar. This indicated that D- and L-theanine may exhibit a competitive effect with respect to intestinal absorption. Regardless of the route of administration, p.o. or i.p., the presence of the other enantiomer always decreased theanine plasma concentrations, indicating D,L-theanine competition with respect to urinary reabsorption. Data on urinary concentrations of D-theanine suggested that the D-isomer may be eliminated with minimal metabolism. L-Theanine appeared to be preferentially reabsorbed and metabolized by the kidney while D-theanine was preferentially excreted. Clearly, the bioequivalencies of D,L-theanine and its enantiomers were found to be quite different from one another. Consequently, the efficacy of commercial theanine products containing D-theanine, L-theanine, or D,L-theanine may be quite different.
authors.affiliation: Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Meera J
authors.initials: MJ
authors.lastname: Desai
authors.forename: Manmeet S
authors.initials: MS
authors.lastname: Gill
authors.forename: Walter H
authors.initials: WH
authors.lastname: Hsu
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Armstrong
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid; D005971:Glutamates / Q000097:blood / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D008297:Male; D013058:Mass Spectrometry; D051381:Rats; D017207:Rats, Sprague-Dawley; D013237:Stereoisomerism
chemical_list: D005971:Glutamates; C026166:theanine