![]() Theanine is substantially present in black, green, and white teas from Camellia sinensis in quantities of about 1% of the dry weight. It was discovered as a constituent of tea ( Camellia sinensis) in 1949, and in 1950 a laboratory in Kyoto successfully isolated it from gyokuro leaf, which has high theanine content. Theanine is found primarily in plant and fungal species. Amino acid racemization in aqueous media is a well-established chemical process promoted by elevated temperature and non-neutral pH values prolonged heating of Camellia extracts-possible for oversteeped teas and in undisclosed commercial preparative processes-has been reported to result in increasing racemization of theanine to give increasing proportions of the nonnatural D-theanine, up to equal proportions of each enantiomer. While natural extracts that are not harshly treated are presumed to contain only the biosynthetic L- enantiomeric form, mishandled isolates and racemic chemical preparations of theanines necessarily contain both theanine and its D-enantiomer (and from racemic syntheses, in equal proportion), and studies have suggested that the D-isomer may actually predominate in some commercial supplement preparations. Relative to theanine, the opposite ( D-, R-) enantiomer is largely absent from the literature, except implicitly. Theanine is a derivative of glutamine that is ethylated on the amide nitrogen (as the name N 5-ethyl- L-glutamine describes), or alternatively, to the amide formed from ethylamine and L-glutamic acid at its γ- (5-) side chain carboxylic acid group (as the name γ-L-glutamylethylamide describes). Theanine is an analog of this amino acid, and its primary amide, L- glutamine (also a proteinogenic amino acid). The name theanine, without prefix, is generally understood to imply the L- ( S-) enantiomer, derived from the related proteinogenic L-amino acid glutamic acid. The chemical name N 5-ethyl- L-glutamine and other synonyms (see box) for theanine reflect its chemical structure. The European Food Safety Authority found there was insufficient evidence for a cause-and-effect relationship between theanine consumption and improved cognitive function, alleviation of psychological stress, maintenance of normal sleep, or reduction of menstrual discomfort. Theanine is sold as a dietary supplement and is considered to be safe at doses up to 250 milligrams (mg) by the US Food and Drug Administration. The opposite enantiomer, D-theanine, has been studied less. The name theanine without a prefix generally implies the enantiomer, L-theanine, which is the form found in tea leaves and as a dietary supplement ingredient. Theanine provides a unique brothy or savory ( umami) flavor to green tea infusions. It constitutes about 1–2% of the dry weight of green tea leaves. ![]() ![]() It was discovered as a constituent of green tea in 1949 in 1950, it was isolated from gyokuro leaves. Theanine / ˈ θ iː ən iː n/, also known as L-γ-glutamylethylamide and N 5-ethyl- L-glutamine, is an amino acid analogue of the proteinogenic amino acids L-glutamate and L-glutamine and is found primarily in particular plant and fungal species.
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