Aporphine alkaloids
Aporphine alkaloids are naturally occurring chemical compounds from the group of alkaloids. After the benzylisoquinoline alkaloids they are the second largest group of isoquinoline alkaloids.
Up to now, 85 aporphine alkaloids have been isolated from plants of 15 families; the best known representative is apomorphine. The aporphine alkaloids are of interest mainly because of their similarity to morphine.
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Occurrence
The aporphine alkaloids are most commonly found in plants.
For example, isoboldine can be found in the plants Beilschmiedia, Nandina (Nandina domestica), Horn poppy (Glaucium) and other plants. As the name suggests, glaucine was first found in the horn-poppy (glaucium) and usually the name of the alkaloids is derived from the plants in which they were first found.
Corydin as a further representative of the aporphine alkaloids is found in the lark spurs (Corydalis), heart flowers (Dicentra) and also in the horny poppy (Glaucium).
Examples
- Apoglaziovine
- Corydine
- Isoboldine
- Isothebaine
The aporphine alkaloids differ in their different substituents and their position on the base structure. Furthermore, their stereochemistry is partly different, most often they are (R)-configured, but e.g. glaucine, bulbocapnine and isothebaine are (S)-configured.[1]
Biosynthesis
Reticulin 1 is oxidized in the first step, resulting in a mesomery-stabilized diradical with the boundary structures 2a and 2b. Cyclization results in a fourth six-membered ring: corytuberin 3, which then dehydrates to bulbocapnin 4.[2] Schematic diagram:
Chemistry
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The aporphine alkaloids are of particular interest because of their proximity to morphine and benzylisoquinoline alkaloids. For example, as the name suggests, morphine can be used to produce apomorphine. This can be done by adding an acid under the influence of heat.
The proaporphin alkaloids and the aporphin alkaloids share a framework isomerism.
The aporphine alkaloids usually have a stereocentre.
The (R)-configured glaucine can be synthesized from (S)-glaucine.
Use
Apomorphine lowers blood pressure and is also a powerful emetic. It is mainly used as a remedy for Parkinson's disease because of its stimulating effect on dopamine receptors.[3]
In African traditional medicine, the plant Cassytha (Cassytha filiformis) is considered a medicine against cancer. A study showed that the plant contains many aporphine alkaloids and that the three main alkaloids actinodaphnin, cassythin and dicentrin have an indeed in vitro effect on cancer cells.[4]
Literature
- Geoffrey A. Cordell: Introduction to Alkaloids: A Biogenetic Approach. John Wiley & Sons, Kanada 1981, ISBN 0-471-03478-9.
References
- K. W. Bentley, H. M. E. Cardwell: The Morphine-Thebaine group of alkaloids. Part V. The absolute stereochemistry of the morphine, benzylisoquinoline, aporphine, and tetrahydroberberine alkaloids. In: Journal of the Chemical Society. Oxford 1955, S. 3252–3260, doi:10.1039/JR9550003252.
- G. Blaschke: Mechanismusder Diphenylverknüpfung bei der Biosynthese von Aporphin-Alkaloiden. 3. Mitt.: Untersuchung zur Biosynthese von Alkaloiden. In: Archiv der Pharmazie. 303 (4), 1970, S. 358–363, doi:10.1002/ardp.19703030411.
- Geoffrey A. Cordell: Introduction to Alkaloids: A Biogenetic Approach. John Wiley & Sons, Kanada 1981, ISBN 0-471-03478-9, S. 406–408.
- S. Hoet, C. Stevigny, S. Block, F. Opperdoes, P. Colson, B. Baldeyrou, A. Lansiaux, C. Bailly, J. Quetin-Leclercq: Alkaloids from Cassytha filiformis and related aporphines: antitrypanosomal activity, cytotoxicity, and interaction with DNA and topoisomerases. In: Planta Med. 70 (5), Thieme Verlag, Stuttgart 2004, S. 407–413, doi:10.1055/s-2004-818967.