Alkaloid
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222038478
2008-06-27T07:42:43Z
Bodragon
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"Alkaloid are" to "Alkaloids are"
[[Image:Ephedrine.png|thumb|Chemical structure of [[ephedrine]], a phenethylamine alkaloid]]
'''Alkaloids''' are naturally occurring [[chemical compound]]s containing [[base (chemistry)|basic]] [[nitrogen]] atoms. The name derives from the word [[alkaline]] and was used to describe any nitrogen-containing base. Alkaloids are produced by a large variety of organisms, including [[bacteria]], [[fungus|fungi]], [[plant]]s, and [[animal]]s and are part of the group of [[natural products]] (also called [[secondary metabolite]]s). Many alkaloids can be purified from crude extracts by [[acid-base extraction]]. Many alkaloids are [[toxicity|toxic]] to other organisms. They often have [[pharmacology|pharmacological]] effects and are used as [[medication]]s and [[recreational drug]]s. Examples are the [[local anesthetic]] and [[stimulant]] [[cocaine]], the stimulant [[caffeine]], [[nicotine]], the [[analgesic]] [[morphine]], or the [[antimalarial drug]] [[quinine]]. Some alkaloids have a [[Bitter (taste)#Bitterness|bitter taste]].
[[Image:Caffeine.svg|180px|thumb|[[Caffeine]]]]
== Alkaloid classifications ==
Alkaloids are usually classified by their common molecular precursors, based on the [[metabolic pathway]] used to construct the molecule. When not much was known about the [[biosynthesis]] of alkaloids, they were grouped under the names of known compounds, even some non-nitrogenous ones (since those molecules' structures appear in the finished product; the opium alkaloids are sometimes called "phenanthrenes", for example), or by the plants or animals they were isolated from. When more is learned about a certain alkaloid, the grouping is changed to reflect the new knowledge, usually taking the name of a biologically-important amine that stands out in the synthesis process.
* [[Pyridine]] group: [[piperine]], [[coniine]], [[trigonelline]], [[arecaidine]], [[guvacine]], [[pilocarpine]], [[cytisine]], [[nicotine]], [[sparteine]], [[pelletierine]].
* [[Pyrrolidine]] group: [[hygrine]], [[cuscohygrine]], [[nicotine]]
* [[Tropane]] group: [[atropine]], [[cocaine]], [[ecgonine]], [[scopolamine]], [[catuabine]]
* [[Quinoline]] group: [[quinine]], [[quinidine]], [[dihydroquinine]], [[dihydroquinidine]], [[strychnine]], [[brucine]], [[veratrine]], [[cevadine]]
* [[Isoquinoline]] group: The [[opium]] alkaloids ([[morphine]], [[codeine]], [[thebaine]], [[Isopapa-dimethoxy-aniline]], [[papaverine]], [[narcotine]], [[sanguinarine]], [[narceine]], [[hydrastine]], [[berberine]]), [[emetine]], berbamine, oxyacanthine
* [[Phenethylamine]] group: [[mescaline]], [[ephedrine]], [[dopamine]], [[amphetamine]]
* [[Indole]] group:
** [[Tryptamine]]s: [[dimethyltryptamine|DMT]], [[N-methyltryptamine]], [[psilocybin]], [[serotonin]]
** [[Ergoline]]s: the [[ergot]] alkaloids ([[ergine]], [[ergotamine]], [[lysergic acid]], [[LSD]] etc.)
** [[Beta-carboline]]s: [[harmine]], [[Harmala alkaloid|harmaline]], [[yohimbine]], [[reserpine]]
** [[Rauwolfia]] alkaloids: [[Reserpine]]
* [[Purine]] group:
** [[Xanthine]]s: [[caffeine]], [[theobromine]], [[theophylline]]
* [[Terpenoid]] group:
** [[Aconite]] alkaloids: [[aconitine]]
** [[Steroid]]s: [[solanine]], [[samandari]]s ([[ammonium|quaternary ammonium compound]]s): [[muscarine]], [[choline]], [[neurine]]
* [[Vinca alkaloids]]: [[vinblastine]], [[vincristine]]. They are antineoplastic and binds free tubulin dimers thereby disrupting balance between microtuble polymerization and delpolymerization resulting in arrest of cells in metaphase.
* Miscellaneous: [[capsaicin]], [[cynarin]], [[phytolaccine]], [[phytolaccotoxin]]
== Physicochemical properties ==
Low-molecular weight alkaloids without [[hydrogen bond]] donors such as [[hydroxy group]]s are often liquid at room temperature, examples are [[nicotine]], [[sparteine]], [[coniine]], and [[phenethylamine]].
The basicity of alkaloids depends on the [[lone pair]]s of electrons on their [[nitrogen]] atoms. As organic bases, alkaloids form salts with [[mineral acid]]s such as [[hydrochloric acid]] and [[sulfuric acid]] and [[organic acid]]s such as [[tartaric acid]] or [[maleic acid]]. These salts are usually more water-[[solubility|soluble]] than their [[free base]] form.
== See also ==
* [[Amine]]
* [[Base (chemistry)]]
* [[Natural products]]
* [[Secondary metabolite]]
{{IPA|}}
== References ==
{{Commons|Alkaloid}}
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