Isoquinoline alkaloids are

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 of the group of

alkaloid 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 ...

s, which are chemically derived from

isoquinoline Isoquinoline is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline. Isoquinoline and quinoline are benzopyridines, which are composed of a benzene ring fused to a pyridine ring. In a broader sense, the term isoquin ...

. They form the largest group among the alkaloids. Isoquinoline alkaloids can be further classified based on their different chemical basic structures. The most common structural types are the benzylisoquinolines and the aporphines.Bettina Ruff: ''Chemische und biochemische Methoden zur stereoselektiven Synthese von komplexen Naturstoffen.'' Verlag Logos, Berlin 2012, , S. 8. () According to current knowledge, a total of about 2500 isoquinoline alkaloids are known nowadays, which are mainly formed by plants.Jennifer M. Finefield, David H. Sherman, Martin Kreitman, Robert M. Williams: ''Enantiomere Naturstoffe: Vorkommen und Biogenese.'' In: ''Angewandte Chemie.'' Wiley-VCH, Weinheim 2012, doi:10.1002/ange.201107204, S. 4905–4915.

Known examples

Morphin - Morphine.svg,

Morphine Morphine is a strong opiate that is found naturally in opium, a dark brown resin in poppies (''Papaver somniferum''). It is mainly used as a analgesic, pain medication, and is also commonly used recreational drug, recreationally, or to make ...

Codein - Codeine.svg,

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 ...

Papaverin - Papaverine.svg,

Papaverine Papaverine (Latin ''papaver'', "poppy") is an opium alkaloid antispasmodic drug, used primarily in the treatment of visceral spasms and vasospasms (especially those involving the intestines, heart, or brain), occasionally in the treatment of erec ...

Berberin.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), '' Hyd ...

Tubocurarine structural formula V2.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 ...

Occurrence in nature

The isoquinoline alkaloids are primarily formed in the plant families of

Papaveraceae The Papaveraceae are an economically important family of about 42 genera and approximately 775 known species of flowering plants in the order Ranunculales, informally known as the poppy family. The family is cosmopolitan, occurring in temperat ...

Berberidaceae The Berberidaceae are a family of 18 genera of flowering plants commonly called the barberry family. This family is in the order Ranunculales. The family contains about 700 known species, of which the majority are in ''Berberis''. The species i ...

Menispermaceae Menispermaceae (botanical Latin: 'moonseed family' from Greek ''mene'' 'crescent moon' and ''sperma'' 'seed') is a family of flowering plants. The alkaloid tubocurarine, a neuromuscular blocker and the active ingredient in the 'tube curare' form ...

Fumariaceae Fumarioideae is a subfamily of the family Papaveraceae (the poppy family). It was formerly treated as a separate family, the Fumariaceae (the fumitory, fumewort or bleeding-heart family). It consists of about 575 species of herbaceous plants in 2 ...

and

Ranunculaceae Ranunculaceae (buttercup or crowfoot family; Latin "little frog", from "frog") is a family of over 2,000 known species of flowering plants in 43 genera, distributed worldwide. The largest genera are ''Ranunculus'' (600 species), ''Delphinium' ...

. The opium poppy, which belongs to the Papavaraceae family, is of great interest, since the isoquinoline alkaloids morphine, codeine, papaverine, noscapine and thebaine can be found in its latex. In addition to the opium poppy, there are other poppy plants, such as the celandine, in which isoquinoline alkaloids are found. Their latex contains berberine, which also occurs in other plant families, such as the Berberidaceae.A. Husemann, T. Husemann: ''Die Pflanzenstoffe in chemischer, physiologischer, pharmakologischer und toxikologischer Hinsicht.'' Berlin 1871, S. 245–253
(Digitalisat Bayerische Staatsbibliothek)
An example of the Berberidaceae with the ingredient berberine is

Berberis vulgaris ''Berberis vulgaris'', also known as common barberry, European barberry or simply barberry, is a shrub in the genus ''Berberis'' native to the Old World. It produces edible but sharply acidic berries, which people in many countries eat as a ta ...

. The alkaloid tubocurarin is found in the hairy cartilage tree. There the Tubocurarin is extracted from the bark and roots.Rudolf Hänsel, Josef Hölzl: ''Lehrbuch der pharmazeutischen Biologie.'' Springer-Verlag, Berlin/ Heidelberg/ New York 2012, 1996, , doi:10.1007/978-3-642-60958-9, S. 302. File:Papaversomniferum.jpg, ''

Papaver somniferum ''Papaver somniferum'', commonly known as the opium poppy or breadseed poppy, is a species of flowering plant in the family Papaveraceae. It is the species of plant from which both opium and poppy seeds are derived and is also a valuable orname ...

'', the opium poppy, contains a wealth of alkaloids, including morphine, codeine and papaverine File:Stylophorum diphyllum durham.jpg, '' Stylophorum diphyllum'', the celandine poppy, contains berberine File:Berberis vulgaris3.jpg, ''

'', the common barberry, contains berberine

Biological effect

In general, isoquinoline alkaloids can have different effects. The opium alkaloids may have

sedative A sedative or tranquilliser is a substance that induces sedation by reducing irritability or excitement. They are CNS depressants and interact with brain activity causing its deceleration. Various kinds of sedatives can be distinguished, but t ...

psychotropic A psychoactive drug, psychopharmaceutical, psychoactive agent or psychotropic drug is a chemical substance, that changes functions of the nervous system, and results in alterations in perception, mood, consciousness, cognition or behavior. Th ...

analgesic An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...

properties.Rainer Nowack: ''Notfallhandbuch Giftpflanzen: Ein Bestimmungsbuch für Ärzte und Apotheker''. Springer-Verlag, Berlin/ Heidelberg 1998, doi:10.1007/978-3-642-58885-3, S. 258. Morphine and codeine are indeed used as analgesics.Jens Frackenpohl: ''Morphin und Opioid-Analgetika.'' In: ''Chemie unserer Zeit.'' WILEY-VCH, Weinheim, 2000, doi:10.1002/1521-3781(200004)34, S. 99–112. Papaverine, in contrast, has an antispasmodic effect if it comes from smooth muscles, as is the case in humans in the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s. This is why it is used as an antispasmodic.Franz v. Bruchhausen, Gerd Dannhardt, Siegfried Ebel, August-Wilhelm Frahm, Eberhard Hackenthal, Ulrike Holzgrabe: ''Hagers Handbuch der Pharmazeutischen Praxis.'' 5. Auflage. Springer-Verlag, Berlin/ Heidelberg 1994, doi:10.1007/978-3-642-57880-9, S. 16. Tubocurarin impairs the transmission of stimuli in the nervous system, so that

paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 50 ...

may occur in the affected organism.Heinz Lüllmann, Klaus Mohr, Lutz Hein: ''Pharmakologie und Toxikologie.'' 16. Auflage. Georg-Thieme Verlag, Stuttgart/ New York 2006, {{ISBN, 3-13-368516-3, S. 255–258.

Known examples

Occurrence in nature

Biological effect

References