Benzylisoquinoline Alkaloid
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Substitution of the heterocycle isoquinoline at the C1 position by a
benzyl group In organic chemistry, benzyl is the substituent or molecular fragment possessing the structure . Benzyl features a benzene ring () attached to a methylene group () group. Nomenclature In IUPAC nomenclature, the prefix benzyl refers to a subst ...
provides 1‑benzylisoquinoline, the most widely examined of the numerous benzylisoquinoline structural
isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...
s. The 1-benzylisoquinoline
moiety Moiety may refer to: Chemistry * Moiety (chemistry), a part or functional group of a molecule ** Moiety conservation, conservation of a subgroup in a chemical species Anthropology * Moiety (kinship), either of two groups into which a society is ...
can be identified within numerous compounds of pharmaceutical interest, such as
moxaverine Moxaverine has been used in therapy based on the direct vasodilatory effect of the drug, a phosphodiesterase inhibitor, and on its influence on the rheological properties of red blood cells. Moxaverine hydrochloride (Kollateral forte®, Ursapha ...
; but most notably it is found within the structures of a wide variety of plant
natural product A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical syn ...
s, collectively referred to as benzylisoquinoline alkaloids. This class is exemplified in part by the following compounds: papaverine, noscapine,
codeine Codeine is an opiate and prodrug of morphine mainly used to treat pain, coughing, and diarrhea. It is also commonly used as a recreational drug. It is found naturally in the sap of the opium poppy, ''Papaver somniferum''. It is typically use ...
, morphine, apomorphine,
berberine Berberine is a quaternary ammonium salt from the protoberberine group of benzylisoquinoline alkaloids found in such plants as ''Berberis vulgaris'' (barberry), ''Berberis aristata'' (tree turmeric), ''Mahonia aquifolium'' (Oregon grape), ''Hydra ...
,
tubocurarine Tubocurarine (also known as ''d''-tubocurarine or DTC) is a toxic alkaloid historically known for its use as an arrow poison. In the mid-1900s, it was used in conjunction with an anesthetic to provide skeletal muscle relaxation during surgery or ...
.


Biosynthesis

(''S'')-
Norcoclaurine Higenamine (norcoclaurine) is a chemical compound found in a variety of plants including ''Nandina domestica'' (fruit), ''Aconitum carmichaelii'' (root), ''Asarum heterotropioides'', '' Galium divaricatum'' (stem and vine), ''Annona squamosa'', ...
( higenamine) has been identified as the central 1-benzyl-tetrahydro-isoquinoline precursor from which numerous complex biosynthetic pathways eventually emerge. These pathways collectively lead to the structurally disparate compounds comprising the broad classification of plant natural products referred to as benzylisoquinoline alkaloids (BIA), which have been comprehensively discussed by Hagel. The biosynthesis of
(S)-norcoclaurine Higenamine (norcoclaurine) is a chemical compound found in a variety of plants including ''Nandina domestica'' (fruit), ''Aconitum carmichaelii'' (root), ''Asarum heterotropioides'', '' Galium divaricatum'' (stem and vine), ''Annona squamosa'', ...
, which is catalyzed by (''S'')-norcoclaurine synthase, is accomplished by the stereoselective condensation of
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic compound, organic chemical of the catecholamine and phenethylamine families. Dopamine const ...
and 4-hydroxyphenylacetaldehyde (4-HPAA); each of these compounds is prepared by multiple enzymatic transformations from L-tyrosine. It is of interest to note that early studies initially identified norlaudanosoline (
tetrahydropapaveroline Tetrahydropapaveroline (norlaudanosoline) is a benzyltetrahydroisoquinoline alkaloid. It can be formed in trace amounts in the brain by a condensation reaction of dopamine and dopaldehyde (a metabolite of dopamine). It inhibits dopamine uptak ...
) as the purported central precursor for the biosynthesis of BIAs. However, more than two decades latter it was finely unequivocally established that (''S'')-norcoclaurine was the central precursor for the biosynthesis of the structurally diverse BIAs.


Examples of benzylisoquinoline alkaloids

File:Benzylisoquinoline structure in Papaverin.svg, Papaverine File:Benzylisoquinoline structure in Noscapine.svg, Noscapine File:Benzylisoquinoline structure in Apomorphone.svg, Apomorphine ''(one additional ring closure)'' File:Benzylisoquinoline structure in Morphine.svg, Morphine ''(two additional ring closures)'' File:Benzylisoquinoline structure in Berberine.svg,
Berberine Berberine is a quaternary ammonium salt from the protoberberine group of benzylisoquinoline alkaloids found in such plants as ''Berberis vulgaris'' (barberry), ''Berberis aristata'' (tree turmeric), ''Mahonia aquifolium'' (Oregon grape), ''Hydra ...
''(one additional ring closure with incorporated N-methyl)'' File:Benzylisoquinoline structures in Tubocurarine.svg,
Tubocurarine Tubocurarine (also known as ''d''-tubocurarine or DTC) is a toxic alkaloid historically known for its use as an arrow poison. In the mid-1900s, it was used in conjunction with an anesthetic to provide skeletal muscle relaxation during surgery or ...
''(composed of two benzylisoquinoline units)''


See also

*
Morphinan Morphinan is the prototype chemical structure of a large chemical class of psychoactive drugs, consisting of opiate analgesics, cough suppressants, and dissociative hallucinogens, among others. Structure Morphinan has a phenanthrene core stru ...
* Indole * Indolizidine


References

{{Reflist
Benzylisoquinoline biosynthesis by cultivated plant cells and isolated enzymes
Alkaloids