Kafeina: Perbedaan antara revisi
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Menurut salah satu legenda populer Cina, [[Kaisar Cina]] [[Shénnóng]], yang dimitoskan telah berkuasa sekitar tahun 3000 SM, tanpa sengaja menemukan bahwa ketika beberapa dedaunan jatuh ke dalam air mendidih, minuman yang wangi dan dapat memulihkan tenaga dihasilkan.<ref>Chow p. 19–20 (Czech edition); also Arcimovicova p. 9, Evans p. 2 and others</ref> Shennong juga disebut-sebut dalam karya Lu Yu, ''[[Cha Jing]]'', mengenai teh.<ref>{{cite book|last = Yu|first = Lu|title = The Classic of Tea: Origins & Rituals|publisher = Ecco Pr; Reissue edition |month=October|year=1995|isbn=0-88001-416-4}}</ref> Sejarah kopi pun telah tercatat sejak abad ke-9. Pada saat itu, biji kopi hanya tersedia dari habitat aslinya saja, [[Etiopia]]. Legenda populer menceritakan penemuan kopi oleh seorang penggembala kambing bernama Kaldi yang memantau bahwa kambing-kambingnya menjadi lebih aktif dan tidak tidur pada malam hari setelah merumputi semak-semak kopi. Setelah ia mencoba buah kopi yang dimakan oleh kambingnya, ia juga mendapatkan khasiat yang sama. Literatur paling awal yang menyebutkan adanya kopi kemungkinan adalah sebuah referensi mengenai Bunchum dalam karya seorang Persia [[al-Razi]]. Pada tahun 1587, [[Malaye Jaziri]] menyusun suatu karya yang menilik sejarah dan kontroversi hukum kopi berjudul "Undat al safwa fi hill al-qahwa". Dalam karyanya ini, Jaziri mencatat bahwa seorang [[Sheikh]], Jamal-al-Din al-Dhabhani, [[mufti]] [[Aden]], adalah yang pertama menggunakan kopi pada tahun 1454, dan pada abad ke-15, para Sufi [[Yaman]] secara rutin menggunakan kopi untuk terus terbangun selama berdoa.
==Sintesis dan ciri-ciri kafeina==
[[File:Caffeine USP.jpg|thumb|Kafeina [[anhidrat]] (kering).]]
Pada tahun 1819, kimiawan [[Jerman]] [[Friedlieb Ferdinand Runge]] berhasil mengisolasi kafeinan yang relatif murni untuk pertama kalinya.<ref>Friedlieb Ferdinand Runge, ''Neueste phytochemische Entdeckungen zur Begründung einer wissenschaftlichen Phytochemie'' [Latest phytochemical discoveries for the founding of a scientific phytochemistry] (Berlin, Germany: G. Reimer, 1820). In Chapter 6 ([http://books.google.com/books?id=KLg5AAAAcAAJ&pg=P146&lpg=P146#v=onepage&q&f=false pages 144–159]), Runge details his (partial) isolation of caffeine, which he calls "Kaffebase" (i.e., a base (alkaline substance) that exists in coffee).</ref><ref>In 1821, caffeine was isolated both by French chemist [[Pierre Jean Robiquet]] and by a pair of French chemists, [[Pierre Joseph Pelletier|Pierre-Joseph Pelletier]] and [[Joseph Bienaimé Caventou]], according to Swedish chemist [[Jöns Jacob Berzelius]] in his yearly journal, ''Jahres-Bericht über die Fortschritte der physischen Wissenschaften von Jacob Berzelius'' [Annual report on the progress of the physical sciences by Jacob Berzelius] (Dr. F. Wöhler, trans.), vol. 4, [http://books.google.com/books?id=XJI8AAAAIAAJ&pg=RA1-PA180&lpg=RA1-PA180#v=onepage&q&f=false page 180], 1825. Furthermore, Berzelius stated that the French chemists had made their discoveries independently of any knowledge of Runge's work or of each other's work. Berzelius states on page 180: "Cafein is eine Materie im Kaffee, die zu gleicher Zeit, 1821, von Robiquet und [von] Pelletier und Caventou entdekt wurde, von denen aber keine etwas darüber im Drucke bekannt machte." (Caffeine is a substance in coffee, which simultaneously, in 1821, was discovered by Robiquet and by Pelletier and Caventou, by whom however nothing was made known about it in print.)<br /><br />In Pelletier's article on caffeine – "Cafeine", [http://books.google.com/books?id=rFw_AAAAcAAJ&pg=PA35#v=onepage&q&f=false pages 35–36] in ''Dictionnaire de Médecine'' (Paris, France: Béchet Jeune, April 1822), vol. 4 – Pelletier himself corroborates Berzelius's account: "Cafeine, s. f. Principe cristallisable décovert dans le café en 1821 par M. Robiquet. A la mème époque, cherchant la quinine dans le café, parce que le café, considéré par plusieurs médecins come fébrifuge, est d'ailleurs de la mème famille que le quinquina, MM. Pelletier et Caventou obtenaient de leur côté la cafeine; mais leur recherches n'ayant qu'un but indirect, et n'ayant pas été terminées, laissent à M. Robiquet la priorité sur cet objet. Nous ignorons pourquoi M. Robiquet n'a pas publié l'analyse du café qu'il a lue à la société de pharmacie. Sa publication nous aurait permis de mieux faire connaître la cafeine, et de donner des idées exactes sur la composition du café...." (Caffeine, noun (feminine). Crystalizable substance discovered in coffee in 1821 by Mr. Robiquet. During the same period – while they were searching for quinine in coffee because coffee is considered by several doctors to be a medicine that reduces fevers and because coffee belongs to the same family as the cinchona [quinine] tree – on their part, Mssrs. Pelletier and Caventou obtained caffeine; but because their research had a different goal and because their research had not been finished, they left priority on this subject to Mr. Robiquet. We will ignore why Mr. Robiquet has not published the analysis of coffee which he read to the Pharmacy Society. Its publication would allow us to make caffeine better known and give us accurate ideas of coffee's composition .... )<br /><br />In Robiquet's article on coffee – "Cafe," [http://cnum.cnam.fr/CGI/gpage.cgi?p1=50&p3=8KY1.4%2F100%2F464%2F0%2F0 pages 50–61] in ''Dictionnaire Technologique, ou Nouveau Dictionnaire Universel des Arts et Métiers'', ... (Paris, France: Thomine et Fortic, 1823), vol. 4 – Robiquet gives an account of his research on coffee on pages 54–56, detailing the extraction of caffeine and its properties on pages 55–56.<br /><br />Pelletier's elemental analysis of caffeine appears on [http://books.google.com/books?id=-BIAAAAAMAAJ&pg=PA182&lpg=PA182#v=onepage&q&f=false pages 182–183] of the article: Dumas and Pelletier (1823) "Recherches sur la composition élémentaire et sur quelques propriéte's caractéristiques des bases salifiables organiques" (Researchs into the elemental composition and some characteristic properties of organic bases), ''Annales de Chimie et de Physique'', vol. 24, pages 163–191.<br /><br />Berzelius later acknowledged Runge's priority in the extraction of caffeine: ''Jahres-Bericht über die Fortschritte der physischen Wissenschaften von Jacob Berzelius'', vol 7, [http://books.google.com/books?id=iGs1AAAAcAAJ&pg=P270&lpg=P270#v=onepage&q&f=false page 270], 1828. Berzelius stated: "Es darf indessen hierbei nicht unerwähnt bleiben, dass Runge (in seinen ''phytochemischen Entdeckungen'' 1820, p.146-7.) dieselben Methode angegeben, und das Caffein unter dem Namen ''Caffeebase'' ein Jahr eher beschrieben hat, als Robiquet, dem die Entdeckung dieser Substanz gewöhnlich zugeschrieben wird, in einer Zussamenkunft der Societé de Pharmacie in Paris die erste mündliche Mittheilung darüber gab." (However, at this point, it should not remain unmentioned that Runge (in his ''Phytochemical Discoveries'', 1820, pages 146–147) specified the same method and described caffeine under the name ''Caffeebase'' a year earlier than Robiquet, to whom the discovery of this substance is usually attributed, having made the first oral announcement about it at a meeting of the Pharmacy Society in Paris.)</ref> Menurut Runge, ia melakukannya atas perintah [[Johann Wolfgang von Goethe]].<ref name="weinberg">{{cite book|last = Weinberg|first = BA|coauthors = BK Bealer|title = The World of Caffeine|publisher = Routledge|year = 2001|isbn=0-415-92722-6}}</ref> Pada tahun 1827, Oudry mengisolasi "teina" dari teh,<ref>Oudry (March 1827) [http://books.google.com/books?id=cGpEAAAAcAAJ&pg=PA477&lpg=PA477#v=onepage&q&f=false "Note sur la Théine"] (Note on theine), ''Nouvelle Bibliothèque médicale...'', vol. 1, page 477-479. See also: Oudry (1827) "Theïn, eine organische Salzbase im Thee" (Theïn, an organic base in tea), Geiger's ''Magazin für Pharmacie'', vol. 19, pages 49–50.</ref> namun kemudian dibuktikan oleh [[Gerardus Johannes Mulder|Mulder]]<ref>[[Gerardus Johannes Mulder]] (1838) "Über Kaffein und Thein" (On caffeine and theine), ''Journal für praktische Chemie'', vol. 15, pages 280-284.</ref> dan Jobst<ref>Carl Jobst (1838) "Thein identisch mit Caffein" (Theine is identical to caffeine), Liebig's ''Annalen der Chemie und Pharmacie'', vol. 25, pages 63–66.</ref> bahwa teina tersebut merupakan senyawa yang sama dengan kafeina.<ref name="weinberg"/> Struktur kafeina berhasil dipecahkan pada akhir abad ke-19 oleh [[Hermann Emil Fischer]], yang juga merupakan orang yang pertama kali berhasil men[[sintesis total]] senyawa ini.<ref>{{cite web|accessdate=2009-08-03|url=http://nobelprize.org/nobel_prizes/chemistry/laureates/1902/press.html |title=Nobel Prize Presentation Speech by Professor Hj. Théel, President of the Swedish Royal Academy of Sciences|date=December 10, 1902}}</ref>
Semua atom nitrogen kafeina pada dasarnya planar ([[hibridiasi orbital]] sp<sup>2</sup>), menyebabkan molekul kafeina bersifat [[aromatik]]. Karena kafeina dengan mudah didapatkan sebagai produk samping proses dekafeinasi, kafeina biasanya tidak disentesis secara kimiawi.<ref>{{cite web|author = Simon Tilling|publisher = [[Bristol University]]|url = http://www.chm.bris.ac.uk/webprojects2001/tilling/synthesis.htm|title = Crystalline Caffeine|accessdate=2009-08-03}}</ref> Apabila diperlukan, kafeina dapat disintesis dari [[dimetilurea]] dan [[asam malonat]].<ref>{{cite book|title = Beverages in Nutrition and Health|author = Ted Wilson, Norman J. Temple|page = 172|isbn = 1-58829-173-1|publisher = Humana Press|year = 2004}}</ref>
== Metabolisme dan toksisitas ==
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