Cactus alkaloids are

alkaloids Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar st ...

that occur in

cactus A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...

. Structurally, they are tetrahydroisoquinolines and

phenylethylamines 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 amin ...

Occurrence and Representatives

Cactus alkaloids are found in the cactus family, particularly in the genus ''

Lophophora ''Lophophora'' () is a genus of spineless, button-like cacti. Its area range covers southern through northeastern and north-central Mexico to Querétaro in central Mexico. The species are extremely slow growing, sometimes taking up to thirty ye ...

'', 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 amin ...

and tetrahydroisoquinoline, respectively. The primary alkaloid in ''

Lophophora williamsii The peyote (; ''Lophophora williamsii'' ) is a small, spineless cactus which contains psychoactive alkaloids, particularly mescaline. ''Peyote'' is a Spanish word derived from the Nahuatl (), meaning "caterpillar cocoon", from a root , "to gl ...

'' (in terms of quantity) is

mescaline Mescaline or mescalin (3,4,5-trimethoxyphenethylamine) is a naturally occurring psychedelic protoalkaloid of the substituted phenethylamine class, known for its hallucinogenic effects comparable to those of LSD and psilocybin. Biological sou ...

, followed by

pellotine Pellotine is an alkaloid found in ''Lophophora'' species. Pellotine is slightly narcotic, and has been used by Native Americans as a constituent of peyote for sacramental purposes. Psychological and physiological effects 8-10 mg of isolated ...

. In the species ''

Lophophora diffusa ''Lophophora diffusa'', commonly known as false peyote, is a species of plant in the family Cactaceae and one of the only two species in the Lophophora genus. It is endemic to Mexico in the outskirts of Querétaro. This species contains zero to ...

'' and ''

Lophophora fricii ''Lophophora'' () is a genus of spineless, button-like cacti. Its area range covers southern through northeastern and north-central Mexico to Querétaro in central Mexico. The species are extremely slow growing, sometimes taking up to thirty ...

'', the primary alkaloid is pellotine, followed by

anhalonidine Anhalonidine a naturally occurring alkaloid which can be isolated from certain members of the cactus family, such as ''Lophophora''. It is structurally related to mescaline. See also * Anhalamine * Anhalidine * Anhalinine * Gigantine * Pellotine ...

in ''L. fricii'' and

anhalamine Anhalamine is a naturally occurring alkaloid which can be isolated from ''Lophophora williamsii''. It is structurally related to mescaline. See also * Anhalinine * Anhalonidine * Pellotine Pellotine is an alkaloid found in ''Lophophora'' spe ...

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 ''N''-Methyltyramine (NMT), also known as 4-hydroxy-''N''-methylphenethylamine, is a human trace amine and natural substituted phenethylamine, phenethylamine alkaloid found in a variety of plants.T. A. Smith (1977). "Phenethylamine and related c ...

, mescaline, or pellotine. File:Lophophora_williamsii_Blüte.JPG, ''

'' File:2-(3,4,5-trimethoxyphenyl)ethanamine_200.svg,

Mescaline Mescaline or mescalin (3,4,5-trimethoxyphenethylamine) is a naturally occurring psychedelic protoalkaloid of the substituted phenethylamine class, known for its hallucinogenic effects comparable to those of LSD and psilocybin. Biological sou ...

File:Lophophoradiffusa.jpg, ''

'' File:Pellotin_Structural_Formula_V1.svg,

Pellotine Pellotine is an alkaloid found in ''Lophophora'' species. Pellotine is slightly narcotic, and has been used by Native Americans as a constituent of peyote for sacramental purposes. Psychological and physiological effects 8-10 mg of isolated ...

Biosynthesis

The

biosynthesis Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. ...

of cactus alkaloids starts from the

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

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 non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...

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 blood-b ...

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 compound, organic chemical of the catecholamine and phenethylamine families. Dopamine const ...

. By introducing a third hydroxy group and

methylation In the chemical sciences, methylation denotes the addition of a methyl group on a substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replacing a hydrogen atom. These t ...

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

and

. Anhalonidine is the biosynthetic precursor of anhalonine, in which a

benzodioxole 1,3-Benzodioxole (1,2-methylenedioxybenzene) is an organic compound with the formula CHOCH. The compound is classified as benzene derivative and a heterocyclic compound containing the methylenedioxy functional group. It is a colorless liquid. Alt ...

unit is formed from a hydroxyl and a methoxy group. Further branching of the biosynthetic pathways occurs through the methylation of the amino group from dopamine. This pathway leads to

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 Anhalamine is a naturally occurring alkaloid which can be isolated from ''Lophophora williamsii''. It is structurally related to mescaline. See also * Anhalinine * Anhalonidine * Pellotine Pellotine is an alkaloid found in ''Lophophora'' spe ...

anhalidine Anhalidine is a naturally occurring tetrahydroisoquinoline based alkaloid which can be isolated from ''Lophophora williamsii The peyote (; ''Lophophora williamsii'' ) is a small, spineless cactus which contains psychoactive alkaloids, partic ...

, and

can be synthesized starting from

, among others.

Pharmacological Effect

is a

psychedelic Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary states of consciousness (known as psychedelic experiences or "trips").Pollan, Michael (2018). ''How to Change Your Mind: What the New Science of ...

and is responsible for the hallucinogenic properties of ''

'' (''peyote''). The other alkaloids predominantly exhibit much less pronounced pharmacological effects and may have anticonvulsant properties.

was briefly used as a sedative in the early 20th century.

References

{{Reflist Alkaloids