LOBELIACEAE

The Lobeliaceae is a family of about 25 genera of mainly herbs, mostly native to tropical regions. Leaves are alternate, sometimes in rosettes and without stipules. Flowers may be solitary or in racemes, spikes or panicles. Calyx and corolla both 5-lobed and the corolla petals are variously united, 1 or 2 lipped. There are 5 stamens and the fruit is fleshy and berrylike or a capsule containing many small seeds.

Lobelia inflata [Restricted Herb]

Lobelia, Indian tobacco

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Family Lobeliaceae

Description

A hairy annual or biennial, often branched herb, 15–45 cm tall in flower. Basal leaves obovate to lanceolate, serrate, usually less than 7 cm long, hairy beneath. Stem leaves alternate, sessile, becoming smaller up the stem. Flowers small, inconspicuous, solitary, in racemes in the axils of the upper leaves. Corolla white to pale blue. The calyx tube inflates to 1.5 cm after the flower dies, enclosing the capsule containing many tiny, rough seeds. Flowers from mid summer onwards.

Habitat and cultivation

Lobelia is native to North America in fields, waste places and open woods from Nova Scotia to Georgia, Arkansas, east Kansas and north to Saskatchewan. It was introduced to other countries and is always grown from seed sown in autumn or spring and will self-sow in open sunny situations. Drought and frost resistant.

Parts used

The herb gathered when the lower fruits are nearly ripe.

Active constituents

1) Alkaloids over 20 of the piperidine type (0.2–0.6%) mainly lobeline also lobelanine, lobelanidine and allosedamine1

2) Carboxylic acids—chelidonic acid

3) Bitter glycoside—lobelacrin

Also contains a derivative of β-amyrin,2 volatile oil, resin and gum.

Nutritional constituents

Vitamins: C

Minerals: Magnesium, phosphorus, potassium and calcium

Actions

1) Respiratory stimulant

2) Expectorant

3) Emetic

4) Spasmolytic

5) Diaphoretic

6) Anti-asthmatic

Scientific information

Lobelia has been an official medicine,4 was used widely in North America and had enjoyed a prized place in herbal medicine as a respiratory stimulant but its effects were apparently unpredictable and it fell out of favour.3 It was called Indian tobacco because it was smoked by Native Americans to get the same effect as that derived from nicotine in tobacco. It is now a restricted herb.

Lobeline, the main active alkaloid, has similar actions to nicotine, binding to the same receptor sites in nerve cells (nicotinic agonist) although it can also act as a nicotinic antagonist.3 It is a neural depressant for autonomic, central and neuromuscular synapses although its initial effect is stimulating.4 Lobeline stimulates the cough reflex,5 is a respiratory stimulant (has been used to counter respiratory depression from narcotic overdose), broncho-relaxant, aid to expectoration, has cholinergic properties, increases dopamine levels, is emetic, may increase mucosal and lacrimal secretions, has mild appetite suppressant properties6 and may be of use in the treatment of psycho-stimulant abuse.7 However it has low bioavailability unless it is absorbed through the sublingual mucosa.

Medicinal uses

Lobelia is used for treating:-

Externally used as a lotion for:-

Externally as a plaster for:-

Precautions and/or safety

Lobelia in large doses can have side effects including diarrhoea, increased diuresis, nausea, vomiting, increased sweating, paresis, tachycardia, hypotension and coma. Over dosing is however rare as it induces vomiting and no fatalities due to it alone have been recorded.8