Tobacco alkaloids lobeline

Lobelia inflata (Indian tobacco) contains lobeline and other pyridine alkaloids. It has been used as an emetic, antidepressant, respiratory stimulant, an aid to smoking cessation, and a treatment for metamfetamine abuse (1). 

Thebaine, the methoxy derivative of morphine, is also a habit-forming substance, but its primary toxic effects are similar to those of strychnine, a convulsant poison, rather than narcosis. Also, there are alkaloids having different structures but similar toxic actions. Lobeline, a lobelia alkaloid, which has a piperidine nucleus, shows pharmacologic action similar (but less potent) to that of nicotine, a tobacco alkaloid that has a pyridine-pyrrolidine ring system. The structure, occurrence, physical properties, and toxicity of some important alkaloids are presented in the following sections. 

Isolates from Indian tobacco Q obelia inflata L.), as a cmde mixture of bases, have been recognized as expectorants. The same (or similar) fractions were also used both in the treatment of asthma and as emetics. The principal alkaloid in T. inflata is lobeline (49), an optically active tertiary amine which, unusual among alkaloids, is reported to readily undergo mutarotation, a process normally associated with sugars. Interestingly, it appears that the aryl-bearing side chains in (49) are derived from phenylalanine (25, R = H) (40). 

Lobelia or Indian tobacco consists of the dried leaves and tops of Lobelia inflata (Campanulaceae), an annual herb from the USA and Canada. Lobelia contains about 0.2-0.4% of alkaloids, of which the piperidine derivative lobeline (Figure 6.23) is the chief constituent. Minor alkaloids identified include closely related structures, e.g. lobelanine (Figure 6.23). The North American Indians employed lobelia as an alternative or substitute for tobacco (Nicotiana tabacum Solanaceae), and it is found that lobeline stimulates nicotinic receptor sites in a similar way to nicotine, but with a weaker effect. Lobeline has been employed in preparations intended as smoking deterrents. The crude plant drug has also long been used to relieve asthma and bronchitis, though in large doses it can be quite toxic. 

Transdermal nicotine is nsed in the relief of nicotine withdrawal symptoms in patients attempting smoking cessation. Two natnral alkaloids, nicotine and lobeline, exhibit peripheral actions by stimnlating antonomic ganglia. Nicotine was hrst isolated from leaves of tobacco, Nicotiana tabacum. Nicotine is of considerable medical signihcance becanse of its toxicity, presence in tobacco, and propensity for conferring a dependence on its nsers. 

Lobelia. Indian tobacco wild tobacco emetic herb asthma wsed bladder pod vomit wort. Dried leaves and tops of Lobelia inflate L., Lobetiaeeae. (The seeds are also used.) Habit. Canada, U.S. ConstiL Leaves and lops chiefly lobeline, also lobelidine, lobelanine, lobelamdine. and other alkaloids. Seeds lobeline, fixed oil. 

Lobeline is the principal lobelia alkaloid. It occurs in the seeds and herb of Indian tobacco (Lobelia inflata and Lobeliaceae). It is used as a respiratory stimulant. Its sulfate salt is used in antismoking tablets. 

L. inflata (Indian tobacco) is indigenous to the Eastern and Central states of USA and Canada. The plant contains ca. 0.3% of alkaloids. The L. a. are 2,6-di-substituted piperidine derivatives. Among the ca. 20 L. a., lobeline is the major alkaloid. When administered parenterally (3-10 mg) lobeline stimulates respiration and was used in the past as a respiratory analeptic agent for asthma, collapse, and narcosis incidents. When taken orally it is rapidly degraded and thus not effective. Since lobeline potentiates the action of nicotine and induces nausea and revulsion it has been developed clinically in depot form in antismoking preparations. - The piperidine ring is biogenetically derived from lysine and the substituents from phenylalanine. 

Another series of lysine derived alkaloids occurs in the genus Lobelia (Campanulaceae). One of these compounds, lobeline (39) (Fig. 29.13) (from Lobelia inflata, Indian tobacco), has been used in antismoking preparations. Both lobeline and nicotine are classed as ganglionic stimulants. Therapeutically, lobeline is hardly used today (Fodor and Colosanti, 1985). Poisoning of cattle because of ingestion of Lobelia berlandieri has occurred in Texas and Mexico... 

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