Alkaloids


Alkaloids have complex ring structures containing nitrogen. Some plants produce alkaloids as part of its defence system to protect themselves from diseases and pests. Why plants produce alkaloids still remains as a question but various theories proposed that they are by-products of normal plant metabolism. The presence of alkaloids may not be due to a specific reason and may have multiple purposes to be synthesised in plants. For example, alkaloids may be a reservoir for molecules that plants often use. Plants that synthesise alkaloids include seed-bearing plants such as berries and alkaloids are normally deposited in the bark, fruit, roots, and leaves. Often, they are bases thus tastes bitter but most importantly the physiological effects play a fundamental roles for today’s medicinal uses. Some commonly seen alkaloids for medical purposes are illustrated as follow.

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The opium poppy contains a variety of alkaloids and Morphine is one of them, which is practically used as painkiller. It is often given to patients before surgery as anaesthetic or for immediate relieve of pains. Codeine, similar in structure to morphine, is also obtained from the poppy, also helps to relieve pain. Heroin is a synthetic derivative of morphine that is highly addictive. It exhibited a relaxing effect which is commonly describe as feeling “high” if given to mammals.

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Other members of alkaloids include quinine, cocaine and lysergic acid. Natural source of quinine is derived from Quechua, also known as Cinchona tree bark. Quinine was indeed a very important medicine for the treatment of malaria. It is effective to halt shivering due to cold temperature of malaria disease and its anti-malaria properties are essential for muscle relaxant.
(Seeman, 2007)
Lysergic acid is produced by a type of fungus that grows on rye. A synthetic variation of this compound called lysergic acid diethylamide is a powerful hallucinogen called LSD. Another class of alkaloids are based on structures called piperidine rings. These include compounds such as cocaine. Cocaine is a powerful stimulant that can be addictive like heroin.
(Cordell, 2002)

References

Cordell, G. A. (Ed.). (2002). The alkaloids (58th ed.). San Diego, California, USA: Elsevier Science.
Seeman, J. I. (2007). Review paper on: The woodward-Doering/Rebe-Kindles total synthesis of quinine: setting the record straight. J Angew Chem Int. 46, 1378-1413.