Cactus alkaloids are

alkaloids Alkaloids are a broad class of naturally occurring organic compounds that contain at least one nitrogen atom. Some synthetic compounds of similar structure may also be termed alkaloids. Alkaloids are produced by a large variety of organisms i ...

that occur in

cactus A cactus (: cacti, cactuses, or less commonly, cactus) is a member of the plant family Cactaceae (), a family of the order Caryophyllales comprising about 127 genera with some 1,750 known species. The word ''cactus'' derives, through Latin, ...

. Structurally, they are tetrahydroisoquinolines and phenylethylamines.

Occurrence and Representatives

Cactus alkaloids are found in the cactus family, particularly in the genus '' Lophophora'', which alone contains over 40 known compounds. The alkaloids can be categorized into two groups, derived from

phenethylamine Phenethylamine (PEA) is an organic compound, natural monoamine alkaloid, and trace amine, which acts as a central nervous system stimulant in humans. In the brain, phenethylamine regulates monoamine neurotransmission by binding to trace ami ...

and tetrahydroisoquinoline, respectively. The primary alkaloid in '' Lophophora williamsii'' (in terms of quantity) is

mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...

, followed by pellotine. In the species '' Lophophora diffusa'' and '' Lophophora fricii'', the primary alkaloid is pellotine, followed by anhalonidine in ''L. fricii'' and anhalamine in ''L. diffusa''. In species outside the genus ''Lophophora'', the content and variety of cactus alkaloids are significantly lower, but some contain compounds such as hordenine, N-methyltyramine, mescaline, or pellotine. A number of psychoactive cacti are found in the genus Echinopsis, such as the San Pedro cactus. File:Lophophora williamsii Blüte.JPG, '' Lophophora williamsii'' File:2-(3,4,5-trimethoxyphenyl)ethanamine 200.svg,

Mescaline Mescaline, also known as mescalin or mezcalin, and in chemical terms 3,4,5-trimethoxyphenethylamine, is a natural product, naturally occurring psychedelic drug, psychedelic alkaloid, protoalkaloid of the substituted phenethylamine class, found ...

File:Lophophoradiffusa.jpg, '' Lophophora diffusa'' File:Pellotin Structural Formula V1.svg, Pellotine File:Troncos de cactus Echinopsis pachanoi.jpg, ''

Echinopsis pachanoi ''Trichocereus macrogonus'' var. ''pachanoi'' (Synonym (taxonomy), synonyms including ''Trichocereus pachanoi'' and ''Echinopsis pachanoi'') is a fast-growing columnar cactus found in the Andes at in altitude. It is one of a number of kinds of ...

Biosynthesis

The

biosynthesis Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-Catalysis, catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthe ...

of cactus alkaloids starts from the

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is ...

and proceeds initially via

tyramine Tyramine ( ) (also spelled tyramin), also known under several other names, is a naturally occurring trace amine derived from the amino acid tyrosine. Tyramine acts as a catecholamine releasing agent. Notably, it is unable to cross the bl ...

and

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...

. By introducing a third hydroxy group and

methylation Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replac ...

of all three hydroxy groups,

is formed. A tetrahydroisoquinoline scaffold can also be constructed from the intermediates of mescaline biosynthesis by a ring closure, resulting in anhalamine and anhalonidine. Anhalonidine is the biosynthetic precursor of anhalonine, in which a benzodioxole unit is formed from a hydroxyl and a methoxy group. Further branching of the biosynthetic pathways occurs through the methylation of the

amino group In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

from dopamine. This pathway leads to pellotine and subsequently to lophophorin.

Synthesis

Various synthetic methods for cactus alkaloids are known. In the case of tetrahydroisoquinoline compounds, the ring system is usually built up by a Bischler-Napieralski reaction. Anhalamine, anhalidine, anhalonidine, and pellotine can be synthesized starting from

, among others.

Pharmacological Effect

is a psychedelic and is responsible for the hallucinogenic properties of '' Lophophora williamsii'' (''peyote''). The other alkaloids predominantly exhibit much less pronounced pharmacological effects and may have anticonvulsant properties. Pellotine was briefly used as a sedative in the early 20th century.

References

{{Reflist Alkaloids