|
|Section2= |Section3= }} Hordenine (''N'',''N''-dimethyltyramine) is an alkaloid of the phenethylamine class that occurs naturally in a variety of plants, taking its name from one of the most common, barley (''Hordeum'' species). Chemically, hordenine is the ''N''-methyl derivative of ''N''-methyltyramine, and the ''N'',''N''-dimethyl derivative of the well-known biogenic amine tyramine, from which it is biosynthetically derived and with which it shares some pharmacological properties (see below). Currently,〔September, 2012.〕 hordenine is widely sold as an ingredient of nutritional supplements, with the claims that it is a stimulant of the central nervous system, and has the ability to promote weight loss by enhancing metabolism. In experimental animals, given sufficiently large doses ''parenterally'' (i.e. by injection), hordenine does produce an increase in blood pressure, as well as other disturbances of the cardio-vascular, respiratory and nervous systems. These effects are generally not reproduced by ''oral'' administration of the drug in test animals, and there are virtually no scientific reports of the effects of hordenine in human beings. More detailed discussions of hordenine pharmacology and toxicology are given below. ==Occurrence== The first report of the isolation from a natural source of the compound which is now known as hordenine was made by Arthur Heffter in 1894, who extracted this alkaloid from the cactus ''Anhalonium fissuratum'' (now reclassified as ''Ariocarpus fissuratum''), naming it "anhalin".〔A. Heffter (1894). "Ueber Pellote." ''Arch. exp. Path. Pharmakol.'' 34 65-86.〕 Twelve years later, E. Léger independently isolated an alkaloid which he named hordenine from germinated barley (''Hordeum vulgare'') seeds.〔E. Léger (1906). "Sur l'hordenine: alcaloide nouveau retiré des germes, dits touraillons, de l'orge." ''Compt. Rend.'' 142 108-110.〕 Ernst Späth subsequently showed that these alkaloids were identical and proposed the correct molecular structure for this substance, for which the name "hordenine" was ultimately retained.〔E. Späth (1919). "Über die Anhalonium-Alkaloide. I. Anhalin und Mezcalin." ''Monatschefte für Chemie'' 40 129-154.〕 Hordenine is present in a fairly wide range of plants, notably amongst the cacti,〔(www.erowid.org )〕 but has also been detected in some algae and fungi.〔T. A. Wheaton and I. Stewart (1970) ''Lloydia'' 33 244-254.〕〔T. A. Smith (1977). "Phenethylamine and related compounds in plants." ''Phytochem.'' 16 9-18.〕〔J. Lundstrom (1989). "β-Phenethylamines and ephedrines of plant origin." In ''The Alkaloids, Vol. 35" (A. Brossi, Ed.) pp. 77-154.〕 It occurs in grasses, and is found at significantly high concentrations in the seedlings of cereals such as barley (''Hordeum vulgare'') (~ 0.2%, or 2000 μg/g), proso millet (''Panicum miliaceum'') (~ 0.2%), and sorghum (''Sorghum vulgare'') (~0.1%).〔 Reti, in his 1953 review of naturally-occurring phenethylamines, notes that the richest source of hordenine is the cactus ''Trichocereus candicans'' (now reclassified as ''Echinopsis candicans''), which was found to contain 0.5-5% of the alkaloid.〔L. Reti (1953). In ''The Alkaloids'', Vol. III, (R. H. F. Manske and H. L. Holmes, Eds.), pp. 313-338, New York: Academic Press.〕 Since barley, via its conversion to malt, is used extensively in the production of beer, beer and malt have been examined by several groups of investigators for the presence of hordenine. Citing a 1965 study by McFarlane,〔W. D. McFarlane (1965) ''Proc. Europ. Brew. Conv.'' 387.〕 Poocharoen reported that beer contained ~ 12–24 mg/L, wort contained ~11–13 mg/L, and malt contained ~ 67 μg/g of hordenine.〔B. Poocharoen (1983), Ph. D. Thesis, Oregon State University. http://ir.library.oregonstate.edu/xmlui/handle/1957/27227〕 The hordenine content of various malts and malt fractions was extensively studied by Poocharoen himself, who also provided a good coverage of related literature up to 1983. This researcher found a mean concentration of hordenine in raw barley〔The level of hordenine in ungerminated barley is negligible, but rises as germination (the first part of the "malting" process) proceeds.〕 of ~ 0.7 μg/g; in green malts (i.e. barley that had been soaked in water for 2 days then germinated for 4 days), the mean concentration was ~ 21 μg/g, and in kilned malts (i.e. green malts that had been heated in a kiln for 1–2 days) the mean concentration was ~ 28 μg/g. When only green malt roots were examined, their mean content of hordenine was ~ 3363 μg/g, whereas the mean level in kilned malt roots was ~ 4066 μg/g.〔 It has been established that, in barley, hordenine levels reach a maximum within 5–11 days of germination, then slowly decrease until only traces remain after 1 month. Furthermore, hordenine is localized primarily in the roots.〔J. D. Mann and S. H. Mudd (1963) ''J. Biol. Chem.'' 238 381-385.〕 In comparing literature values for hordenine concentrations in "barley" or barley "malt", therefore, consideration should be made of the age and parts of the plant being analyzed: the figure of ~ 2000 μg/g cited in the review by Smith,〔 for example, is consistent with Poocharoen's 〔 figures for the hordenine levels in the ''roots'' of malted barley, but not in "whole" malt, where his figures of 21-28 μg/g are more consistent with McFarlane's figure of ~ 67 μg/g.〔 On the other hand, there is a wide range of variability: a study by Lovett and co-workers of 43 different barley lines found concentrations of hordenine in roots ranging from 1-2625 μg/g fresh weight. These workers concluded that hordenine production was not under significant genetic control, but much more susceptible to environmental factors such as light duration.〔J. V. Lovett, A. H. C. Hoult and O. Christen (1994)."Biologically active secondary metabolites of barley. IV. Hordenine production by different barley lines." ''J. Chem. Ecol.'' 20 1945-1954.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「hordenine」の詳細全文を読む スポンサード リンク
|