Synthesis of potential theanine metabolites, related structures and their affinity for CB receptors

Tea (Camellia sinensis (L.) O. Kuntze) contains up to 1.6% of the rare amino acid L-theanine (1) [1], which has the attribute to change mood and, contrary to caffeine, a relaxing effect [2]. As with other amino acids, metabolic decarboxylation is possible, leading to a derivative of γ-aminobutyric acid (GABA), viz. 4-amino-N-ethyl-butyramide. This in turn could be converted to 4-arachidonyl-N-ethyl-butyramide (2). For 2 and similar structures, we found an affinity for CB1 and CB2 receptors. Cannabinoid receptor ligands are of crucial importance in inflammation and due to this also in carcinogenesis, and show psychopharmacological activity [3,4]. 2 was synthesized starting with aminolyis of

boc-4-aminobutyryl-p-nitrophenyl ester (3) [5] by ethylamine leading to boc-4-aminobutyrethylamide. This was transformed by gaseous hydrogen chloride to 3-ethylcarbamoyl-propyl-amide hydrochloride. From this and arachidonic acid, compound 2 was synthesized. We also synthesized 4-oleoyl-N-ethyl-butyramide, oleoyl and arachidonoyl amides of 5-amino-pentanoic acid ethyl amide and 4-amino-butyric acid ethyl ester. All compounds were tested for displacement of [³H]CP55,940 by scintillation counting, using HEK-293 cells transfected with human CB1 and CB2 receptors. Rates of displacement for 2 were: 44% (CB1, 1µM), 100% (CB1, 10µM), 59% (CB2, 1µM) and 94% (CB2, 10µM).

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References: [1] Afzal, M., et al. (1987) Planta Med. 1: 109–110. [2] Eschenauer, G. et al., (2006) Am. J. Health Syst. Pharm. 63: 26–30. [3] Rukwied, R. et al. (2005) Schmerz 19: 528–534. [4] Krishnamoorthy, S. et al. (2006) Cancer Metastasis Rev. 25: 481–491. [5] Castonguay R. et al., (2002) Bioorg. Med. Chem. 10: 4185–4191.