Lobelanine-Biological Source After lobeline, lobelanine is obtained as the most abundant alkaloid of Lobelia inflata

C. Lobelanine

Biological Source After lobeline, lobelanine is obtained as the most abundant alkaloid of Lobelia inflata L. (Lobeliaceae). (Indian Tobacco, Asthma Weed).

Chemical Structure

cis-2, 2’-(1-Methyl-2, 6-piperidine-diyl) bis [1-phenylethanone], (C₂₂H₂₅NO₂).

Isolation The aqueous layer obtained in step (3), as stated under isolation of lobeline, is subjected to column chromatography and the lobelanine is collected as one of the major fractions.

Characteristic Features

1. It is obtained as rosettes of needles from ether or petroleum ether having mp 99°C.

2. It is freely soluble in acetone, benzene, ethanol, chloroform; and slightly soluble in water and ether.

Identification Tests

1. Lobelanine Hydrochloride (C₂₂H₂₅NO₂.HCl): The crystals obtained from dilute ethanol decomposes at 188°C; it is soluble in chloroform; and slightly soluble in absolute ethanol and cold water.

2. Lobelanine Hydrobromide (C₂₂H₂₅NO₂.HBr): The crystals do not give a sharp mp, but gets decomposed at 188°C.

3. Lobelanine Nitrate (C₂₂H₂₅NO₂.HNO₃): The crystals obtained from dilute ethanol has mp 153-154°C.

4. If differs from Lobeline in lacking OH moiety; and therefore, does not react with nitrous acid nor with benzyl chloride.

5. It being a diketonic compound-forms a dioxime.