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Found in Piper spp. - Piper nigrum (black pepper);
Piper longum (long pepper). Both peppers are of major importance in Ayurvedic medicine. Piperine has been showTi to have hepatoprotective effects though less potent than silymarin [Koul & Kapil 1993].
Arecoline (arecaidine methyl ester)
Found in betel nut derived from the palm Areca catechu, widely used in many countries as a masticant. Areca also contains about 15% tannins.
Found in Lobelia inflata along with lobelanine and lobelanidine. The main ring in lobeline is derived from lysine via piperidine, while the 2 benzene rings it contains derive from phenylalanine via the shikimic-acid pathway [Samuelsson 19921.
Lobelia is a relaxant and bronchodilator originally made famous by Thomson and the Physiomedical school of herbalists, however its use is now mainly restricted to medical practitioners.
This is an example of a bicyclic ring system with the fusion of a benzene and a pyridine ring. Biosynthetically they are related to indole alkaloids since both groups are derived from the same 2 precursors, tryptophan and loganin - a monoterpene iridoid [Samuelsson 1992).
Quinine (6-methoxycinchonine) C20 H24 N2 02
Quinine is found in Peruvian bark - Cinchona spp. (Rubiaceae), a tree which originates in the Andes mountains. The major species used are Cinchona succirubra and C. ledgeriana. Quinidine is the isomer of quinine.
Cinchona bark contains 25 closely related alkaloids, including the main therapeutic alkaloids in this category. The average yield is 6-7% (25% quinine, 5% quinidine).
The bark also contains cinchotannic acid (2-4%) which yields insoluble 'cinchona red'.
Uses of quinine: anti-malarial
skeletal muscle relaxant (treatment cramps)
febrifuge for colds, influenza etc. tonic water - quinine is very bitter.
Uses of quinidine: cardiac arrythmias atrial flutter/ fibrillation
Quinidine depresses myocardial excitability, conduction, velocity and contractility. It is used in the form of quinidine sulphate.
Side effects of quinine drugs:
Tinnitus (‘cinchonism’); skin rash; vertigo; unusual bleeding/bruising; visual disturbances.
Quinoline alkaloids are particularly common amongst plants of the Rutaceae family.
Ruta graveolens or common rue contains 30 known alkaloids of the quinoline type (Harborne & Baxter 1993]. These include arborinine and y-fagarine.
Another Rutaceous plant with a similar alkaloidal spectrum to rue is prickly ash bark - Xanthoxylum spp. Two new quinoline alkaioids isolated from Xanthoxylum simulans were shown to have cytotoxic and antiplatelet activities [Chen et al. 1994].
These alkaloids result from the condensation of a phenylethylamine derivative with a phenylacetaldehyde derivative. Both moieties are derived from the same precursors. The precursors are phenylalanine or tyrosine.
Isoquinoline alkaloids are most frequently found in the Papaveraceae, Berberidaceae and Ranunculaceae families This is a very large class of medicinally active alkaloids,
which for convenience can be divided into the following sub-classifications:
Morphinane alkaloids - morphine, codeine, thebaine (phenanthrene derivatives)
Benzylisoquinolines - papaverine, oxyacanthine, turbocurarine Protoberberines - berberine, hydrastine, palmatine. Protopines - cryptopine, protopine Bcnzophenanthradine- chelidonine, sanguinarine. Ipecac alkaloids - emetine, cephaeline Aporphine alkaloids - boldine
PROPERTIES OF ISOQUINOLINE ALKALOIDS
Reported pharmacological properties include the following: antispasmodic (papaverine) [Martin et al.1993] antimicrobial, antitumor [Wu et al. 19891 antifungal (jatrorrhizine) [Grayer & Harborne 1994] antiinflammatory, cholagogue & hepatoprotective, antiviral, amoebicidal [De Silva 1983) antioxidant (oxyacanthine) [Muller & Ziereis 1994] enzyme inhibitors [ Robinson 1986]
Opium poppy - Papaver somniferum (Papaveraceae) Opium is the dried latex obtained from incisions made in unripe fruits of the opium poppy. The official opium drug is standardized to contain 10% morphine. Opium contains over 40 alkaloids which are usually combined with meconic acid, a signature compound for identifying opium. Some major opium alkaloids are listed below [Kapoor 1995]:
morphine [8-14%] narcotic analgesic & hypnotic noscapine [4-8%] antitussive; no narcosis codeine [2.5%-3.5%] antitussive; mild narcotic and analgesic
papaverine [0.5-1%] smoothe muscle relaxant, antitussive thebaine [0.1-2%] alternative source for synthesis of codeine
Heroin is diacetylmorphine - a synthetic derivative which is more toxic and habit-forming than morphine.
Morphine C17 H19 NO3
Morphine is a complex phenolic compound whose pentacyclic structure is derived from tyrosine. It is analgesic, narcotic and a powerful respiratory depressant which was previously used in cough elixers. Morphine induces euphoria and dependency in some people, anxiety and nausea in others. The CNS effects occur through stimulation of specific receptors. Opiate receptors are widely distributed in animals, they respond to both endogenous transmitters (peptides) and ingested plant alkaloids. The main receptor types arc: