Alkaloids Lobelia

According to Wieland, the typical lobelia alkaloids so far isolated and examined belong to three groups (Table A), all of which can be represented by the general Formula I. 

Lobelia alkaloids, e.g., lobelanine (140), can easily lose one of the side chains. The primary degradation product [141] is further cleaved by a McLafferty rearrangement to [142]. Other key fragments corre-... 

The biosynthesis of Lobelia alkaloids with C4 units at C-2 and C-6 can be accounted for in terms of the pathway shown in Scheme 3, in which it is envisaged... 

Norlobelanidine, C21H27O2N. Lobelanidine is separated from the other Lobelia alkaloids by crystallization of its sparingly soluble hydrochloride (488), and the alcoholic mother liquors contain the hydrochloride of a secondary base. This base, which is optically inactive, melts at 120° and forms a hydrochloride, m.p. 244°, a nitrate, m.p. 179-180°, and a hydriodide, m.p. 211°. Since it is converted by methyl p-toluenesulfonate to lobelanidine and by oxidation with chromic acid to norlobelanine, the base is norlobelanidine. It is obtained as an intermediate product in the synthesis of lobelanidine (486). 

Piperidine alkaloids occur in only a few species of higher plants. However, (S)-pipecolic acid 3 [121] is widely distributed in higher plants, microorganisms and animals. Lobeline 4 is the main constituent of lobelia alkaloids (Lobelia inflata, Campanulaceae). It is a respiratory stimulant in mammals. Pi-perine 5 is the active ingredient in black pepper (Piper nigrum). On hydrolysis it furnishes piperic acid 6 and piperidine (hence its name) [122] ... 

The systematic nomenclature introduced (23) for the Lobelia alkaloids will be followed in this review. Under this system the alkaloids are numbered as shown in A and B. 

H. Smogrovicova, O. Spetkova, and A. Jindra, Biochemistry of Lobelia alkaloids. Abhandl. Deut. Akad. Wiss. Berlin, Kl. Chem., Geol. Biol. 147 (1966) CA 66, 83123 (1967)... 

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. 

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. 

The S. a. are formed biogenetically from lysine via enzyme-bound intermediates. The side chain originates from phenylalanine. Sedamine is accompanied by structurally related piperidine alkaloids such as ( )- pelletierine and 2,6 substituted piperidines of the Lobelia alkaloid type (including sedinine, seda-crine) The acute toxicity of the S. a. is low, unambiguous pharmacological activities have not yet been confirmed. ... 

Biological Activity of Tropane Alkaloids Distribution of Tropane Alkaloids Piperidine Alkaloids Alkaloids from Piper Species Piperine Alkaloids Involving Condensation with Acetate/Malonate Sedum Alkaloids Lobelia Alkaloids Lycopodium Alkaloids Piperidine Alkaloids in Insects Polyketide-Derived Alkaloids Coniine... 

Lobelin (-)-lobelin, cfr-8,10-diphenyl-lobelionol, the main Lobelia alkaloid (see). Structurally, it is a lo-belionol, in which both Rj and R2 are phenyl (-C H ) groups. L. crystallizes as colorless needles, m.p. 130-131 °C, [o]d-43° (c = 1, ethanol). It is isolated from Lobelia inflata, and is used medicinally as a respiratory analeptic. On account of its nicotine-like properties, it is also used in the treatment of smoking addiction. Simultaneous administration of nicotine and L. has an additive effect, leading to nausea and aversion. 

Piperidine alkaloids a group of alkaloids containing the piperidine ring system. Simple P.a. are the alkyl substituted piperidines which occur sporadically. The other P.a. are classified according to their origin, e.g. Coninm alkaloids (see), Punica alkaloids (see), Sedum alkaloids (see) and Lobelia alkaloids (see). These various groups are structurally different and have different mechanisms of biosynthesis. Other P. a. are found in water lilies, and are biosynthesized from mevalonic acid (see Nuphara alkaloids). A de-hydropiperidine structure is present in the Areca alkaloids (see) and the Betalains (see). 

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