PYRIDINE - PIPERIDINE ALKALOIDS

Lec. ( 2 )


PYRIDINE - PIPERIDINE ALKALOIDS

On reduction, the tertiary base, pyridine, is converted into the secondary base, piperidine .These two nuclei form the basis of this group, which is sometirnel divided into three subgroups :

(I) Derivatives of piperidine ,including lobeline from lobelia.

(2) Derivatives of nicotinic acid , including arecoline from areca .

(3) Derivatives of both pyridine and pynolidine, including nicotine from tobacco .

The important alkaloidal drugs and their alkaloids that are classified in this group are areca, arecoline hydrobromide , lobelia ,lobeline and nicotine.

Biosynthesis of Pyridine-Piperidine Alkaloids
,
Tracer studics have shown that ornithine is incorporated
into nicotine by tobacco plants.
This incorporation resuitsi n a symmetric labeling pattern of nicotine .
Nicotine is primarily a product of root metabolism, but the formation of small amounts , as well as subsequent reactions such as the demethylation of nicotine , can occur in the leaves of plants .
Areca
Areca , areca nut , or betel nut is the dried , ripe seed of Areca catechu L.
Areca contains several alkaloids that are reduced pyridine derivatives .
duced pyridinen derivatives. Among them are arecoline, arecaidine, guvacine ,and guvacoline . The total alkaloid content can reach 0.45%.
Arecoline,t he most abundant and physiologically
most active alkaloid, is a liquid occurring to the extent of about 0.2% .
Areca also contains tannin( abourl -15%) , lipids , volatile oils,
and gum. Areca is classified as an anthelmintic in veterinary practice and is employed as a vermicide and taeniafuge.

Lobelia
Lobelia or Indian tobacco consists of the dried leaves and rops of Lobelia inflata L. The drug contains 14 alkaloids, of which lobeline is the major and most important. a pungent volatile oil, resin, lipids, and gum.
Lobeline occurs a colorless crystals that are slightly soluble
in water but readily soluble in hot alcohol. Lobeline produces similar, but weaker, pharmacologic effects to those of nicotine on the peripheral circulation; neuromuscular junctions,
and the central nervous system. For this reason, lobeline sulfate was formerly incorporated in tablets or lozenges that were intended to aid in breaking the tobacco habit (smokingd eterrent) .
The majority of controlled studies showed that Lobeline had only a placebo effect on decreasing the physical craving for cigarettes, so these products were removed from the market.

Nicotine
Nicotine is a pyridine alkaloid obtained from the dried
Leaves of the tobacco plant Nicotiana tabacum L. (Fam. Solanaceae).
Nicotinei s colorless to pale yellow very hygroscopic, oily , volatilel iquid with an unpleasant. pungent odor and a sharp, burning, persistent taste .
Nicotine is a ganglionic ( nicot inic ) cholinergic – receptor agonist with
Complex pharmacologic actions that include effects mediated by binding to rcceptors in autonomic ganglia , the adrenal medulla , the neuromuscular junction, and the brain . Chronic use of nicotine may result in psychologic and physical dependence . As a temporary aid for the cessation of cigarettesmoking , the drug is available in transdermal system , and it also available bound to an ion exchange resin in a chewing gum base . These alternative sources of nicotine help reduce the withdrawal symptoms associated with nicotine addiction.

Professor Dr. Saad Ali Ihsan
Ph.D. In Medicinal & Aromatic Plants