in black and white
Main menu
Home About us Share a book
Biology Business Chemistry Computers Culture Economics Fiction Games Guide History Management Mathematical Medicine Mental Fitnes Physics Psychology Scince Sport Technics

The constituents of medicinal plants - Pengelly A.

Pengelly A. The constituents of medicinal plants - London, 2001. - 109 p.
Download (direct link): theconstituents2001.djvu
Previous << 1 .. 23 24 25 26 27 28 < 29 > 30 31 32 33 34 35 .. 37 >> Next

Stramonium is listed in Schedule 1 - dangerous poisons and 2 - medicinal poisons (containing 0.25% or less of alkaloids calculated as hyoscamine) of the NSW Poisons List. Exceptions are made in preparations for smoking or burning.
Duboisia myoporoides-, D. leichhardtii. Also known as corkwood.
Unlike the pituri (D. hopwoodii), the nicotine containing species that inhabits the central and western regions of Australia, these two tree /shrubs are restricted in their distribution to the east coast and adjacent area. Corkwood leaves contain the highest levels of atropine and tropane alkaloids in the world, and since WW2 have replaced Atropa belladonna and Hyoscymus niger as the leading source of these alkaloids [Barnard 1952; Roddick 1991].
D. myoporoides exists naturally in distinct chemical races, some of which have higher levels of tropane alkaloids. In commercial cultivation a hybrid form of the species has been utilized whose leaves contain up to 7% alkaloids [Roddick 1991; Evans 1990].
Erythroxylon coca (Erythroxylaceae)
Coca leaves are obtained from shrubs/small trees indigenous to South America.
Alkaloids present include cocaine, cinnamylcocaine, tropacocaine, valerine.
Cocaine is the methyl ester of benzoylecgonine, and can be semisynthetically produced from ecgonine [Tyler 19881.
Pharmacology of cocaine
Cocaine is relatively unstable and is more often administered as cocaine hydrochloride which is a more stable form. Cocaine blocks nerve conduction upon local application, hence its employment as an anaesthetic (eg. Novacaine). In large doses it is a cerebral stimulant and narcotic. Its adrenergic action is due to inhibition of reuptake of noradrenaline, creating an amphetamine-like effect, though only for very short duration.
Toxicology of cocaine
Cocaine is quickly absorbed into the lungs, heart and brain with almost instant effects, leading to psychic dependence and tolerance [Tyler 1988]. It causes destruction of mucous membranes such as those of the nose. Coca leaf is chewed by natives, and appears to be relatively harmless in this form.
These are also referred to as ‘lupin’ alkaloids since they were first discovered in Lupinus spp. They occur primarily in the Papillionaceae family. The quinolizidine structure consists of two carbon rings with a shared nitrogen atom. Their precursor is lysine.
The major quinolizidine alkaloids are sparteine found in broome and greater celandine (Chelidonium majus), and cytisine from lupins. Myrine comes from bilberry quinolizidine
{Vaccinium myrtillis) in the Ericaceae family.
Sparteine from Sarothamnus scoparius (Scotch broom).
Sparteine is a tetracyclic, oxygen free alkaloid. It is oxytocic, cardiac stimulant and diuretic. It binds strongly to muscarinic receptors and (less strongly) to nicotinic receptors (Schmeller et al 1994). It is a peripheral vasoconstrictor.
Sparteine has a similar cardiac action to quinidine [Samuelsson 1992]. The action of broom in this regard is sparteine modified by the presence of flavonoids. It has an ergot-like
action on the uterus and has been used as a substitute for ergot drugs. Some sources claim broom is narcotic and it has been used in smoking mixtures, though this practice is considered dangerous.
These alkaloids contain two fused 5-membered rings in which a N atom is common to both rings. A hydrogen atom usually occurs opposite the N atom in the а-position, with a hydroxymethyl substitute at the adjacent C-l position. The precursor is ornithine.
pyrrohzidme These alkaloids are widespread in the Boraginaceae,
Asteraceae and Papillionaceae families, the majority occurring in the mega-genus Senecio, all 1500 species of which are thought to contain them, including the common ragwort (S.jacobeae) (Harborne & Baxter 1993].
PAs have been associated with veno-occlusive disease and herbs which contain them are scheduled and unavailable to herbalists. This includes comfrey (Symphytum нзс spp.); borage (Borago officinalis); coltsfoot
'c ^ H (Tussilago farfara); liferoot (Senecio aureus);
I н lungwort (Pulmonaria officinalis). Alkaloids include
I I symphytine, echimidine.
• С ~~ С СИз
The alkaloids also occur as water soluble N-oxides.
он OH
Few therapeutic effects have been postulated for pyrrolizidine alkaloids. The main interest has been in their toxicity which is dealt with in numerous other publications leg. Bruneton 1995]
A very large group of alkaloids whose basic structure contains a pyrrole ring fused to a benzene ring.
Biosynthesis of pure indoles involves the amino acid tryptophan as precursor, while that of a major sub-group of the indoles, including the Catharanthus and Rauvalfia alkaloids, have a second precursor - the monoterpene iridoid loganin.
The indole alkaloid structures typically involve multiple ring systems, often complex in character. They form the basis of several pharmaceutical drugs as well as some of our most potent hallucinogenic drugs, and include poisonous compounds such as strychnine. Of the indole alkaloids used in medicine and pharmacy, the majority are found in members of the family Apocynaceae (eg. Rauvalfia, Vinca, Catharanthus and Alstonia spp.). Other families in which they occur are the Loganaceae, Rubiaceae and Convovulaceae. Indole alkaloids are represented in the fungal kingdom by the ergot alkaloids and the Psilocybin mushrooms.
Previous << 1 .. 23 24 25 26 27 28 < 29 > 30 31 32 33 34 35 .. 37 >> Next