Lobelia (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Lobelia L.

Protologue: Sp. pl. 2: 929 (1753); Gen. pl. ed. 5: 401 (1754).

Family: Campanulaceae

Chromosome number: x= 7, 14; L. angulata: 2n= 14, 70, L. chinensis: 2n= 42, L. nicotianaefolia: 2n= 28

• Lobelia chinensis Lour.,
• L. nicotianaefolia Roth ex Roem. & Schult.

Lobelia consists of 250-300 species, mostly in the tropics and subtropics, especially in America. In Malesia, 12 species occur in the wild, and 5 species are planted as ornamentals.

L. angulata is not very much used in the region. In Java, the pounded leaves are used for sprue. In Vietnam, the fruits are applied to treat scabies, stomach-ache, infected eyes, and difficult urination. In China, the plant is mainly used to treat irregular menstruation, and spermatorrhoea. In Taiwan, the leaves and young tops of L. angulata are eaten as a vegetable.

L. chinensis is commonly used medicinally in China, Indo-China and Thailand, but not in Malaysia and Java, where it is not very common. In Indo-China, the roots are considered depurative, antirheumatic and antisyphilitic, and are also taken as an anti-inflammatory and for kidney problems. In Thailand, the whole plant is used in alcoholic macerates as a lung tonic, for tuberculosis, asthma, and in the treatment of bloody vomiting. In China, the plant is applied externally as a poultice on swellings, sores and ulcers and as an antidote for bites of snakes, insects or scorpions. A decoction is taken as a diuretic and cathartic. It stimulates respiration, lowers the blood pressure, stops bleeding and reduces swellings.

L. nicotianaefolia is, like L. chinensis, not commonly used in Malesia, although it is found dried in Chinese pharmacies. It is considered poisonous. The dry herb, when handled, is very acrid, and causes irritation to the throat and nostrils like tobacco. The symptoms of poisoning are similar to those of nicotine. In India, an infusion of the leaves is taken as an antispasmodic and externally as a leech repellent. In Vietnam, the crushed leaves or the juice are applied on abscesses and furuncles. The latex causes dermatitis. The seeds are very acrid and used as an insecticide throughout its distribution area.

The North American L. inflata L. ("Indian tobacco") is well known as a medicinal, and has been planted for this purpose in the hills of India. It has been used to relieve spasm in asthma and chronic bronchitis, and also in respiratory failure resulting from anaesthesia, poisoning by narcotics and noxious gases. It is also applied in some cases of urticaria. Formulations containing lobeline sulphate and vitamin B are used as a smoking cessation agent. Taken as a tea or smoked as tobacco, it has a mild euphoric marijuana-like quality. L. syphilitica L., a native of the United States, is cultivated as an ornamental in Peninsular Malaysia but does not grow well there. The North American Indians used a decoction of the roots for syphilis, but later analysis found it valueless. Several other Lobelia species, including L. cardinalis L., L. erinus L. and L. laxiflora Kunth are widely planted as ornamentals, and also contain alkaloids.

The South-East Asian Lobelia are hardly traded.

L. inflata is well known in North America and Europe for its content of piperidine-type alkaloids (0.1-0.6%), which are biochemically derived from the amino acid lysine. The alkaloids can be divided into several groups, the main one being the lobeline-group (e.g. lobeline, lobelanine, lobelanidine), together with the lobinine-group (e.g. lobinine, isolobinine), and other groups which include compounds like 8-10-diethyl lobelidiol, 8-ethyl norlobelol-I, isolobinanidine, lelobanidine I and II, lobelanidinelobelanine, lobinalidine, lobinaline, lobinanidine, 8-methyl-10-ethyl-lobelidiol, 8-methyl-10-phenyl-lobelidiol, norlelobanidine, norlobelanidine and norlobanine. The maximum concentration of alkaloids in L. inflata is reached in plants at the middle of the flowering period in India, and the distribution of lobeline in different plant parts was found to be about 1% in the top of the inflorescence and unripe fruits (including the seeds), 0.4% in leaves and stem, and 0.5% in roots. Lobeline can be classified as a nicotinic agonist; the action of lobeline is similar to nicotine, but weaker. Like nicotine, it acts on the central nervous system, autonomic ganglia and the nerve ends in voluntary muscles. It is a primary stimulant and a secondary depressant. In small doses it produces severe vomiting, sweating and general relaxation. Poisonous reactions including rapid and feeble pulse, fall of temperature and collapse with coma, appear when the drug is not rejected by vomiting. Lobeline was also shown to alter presynaptic dopamine (DA) storage by potently inhibiting DA uptake into synaptic vesicles from the rat striatum. D-amphetamine acts at the level of the synaptic vesicle to alter presynaptic function. In contrast to d-amphetamine, which is equipotent in inhibiting DA uptake and promoting release from the synaptic vesicles, lobeline more potently (28-fold) inhibits DA uptake than it evokes DA release to redistribute presynaptic DA storage.

Decoctions of the aerial parts have been used as an expectorant, but this effect cannot be attributed to lobeline, because of its quick degradation in the body. The active compound is probably isolobinine, which strongly irritates the mucous membranes when administered orally. Effects of the triterpene derivativeβ-amyrin palmitate, isolated from the leaves of L. inflata, were studied on the central nervous system of mice and were compared with those of antidepressant drugs, mianserin and imipramine. The results suggest thatβ-amyrin palmitate has similar properties in some respects to mianserin, and might possess a sedative action.

The aerial parts of L. angulata contain related piperidine alkaloids, such as 1-(2-N-methylpiperidyl)-butan-2-one and 1-(2-N-methylpiperidyl)-pentan- 2-one, together with flavonoids like diosmin, linarin, apigenin 7-O-rutinoside and luteolin 7-O-rutinoside, and the polyacetylene lobetyolin.

L. nicotianaefolia also contains alkaloids of the lobeline group, and samples collected during the rainy season in India contain 0.3-0.4%, while dried samples collected at the end of the rainy season contain 1-1.2% total alkaloids. Lobelanidine is the principal alkaloid, together with nor-lobelanine and to a lesser extent l-lelobanidine. In the Indian Pharmacopoeia, the dried aerial parts of L. nicotianaefolia constitute the drug Lobelia or Lobelia Herba.

Little is known about the phytochemistry of L. chinensis. However, a hot water extract showed antitumour activity in an in vitro test with Ehrlich ascites tumor sarcoma 180 cells. Furthermore, the effects of several synthetic inhibitors of endothelium-derived relaxing factors and an extract of L. chinensis, used in China as antisnake venom, on the biological function of endothelin (ET) are reported. The results showed that inhibiting the production of nitric oxide could stimulate ET release from vascular endothelium, elevate plasma ET and increase blood pressure.

The residues obtained from the ethanol extract of stems, leaves and flowers of L. laxiflora were applied in carrageenan- and cobra venom-induced acute inflammation in mice, and a suppression of paw oedema formation at a dose of 100 mg/kg was established.

L. inflata is commonly used as a substitute for other lobeline-producing Lobelia.

• Annual or perennial herbs, sometimes woody below, rarely arborescent, normally lactiferous.
• Leaves spirally arranged, alternate or in a rosette, simple; petiole present or absent; stipules absent.
• Inflorescence a terminal raceme or panicle, or flowers solitary and axillary; bracts present or absent.
• Flowers 5-merous, normally bisexual; calyx lobes valvate; corolla gamopetalous, zygomorphic, with a dorsal slit almost to the base, limb with 2 dorsal lobes, mostly diverging from the lower 3, which form a trifid whole, lobes valvate in bud, connate to a varying degree; stamens 5, alternate with the corolla lobes, free or adnate to the corolla tube, partly connate with the filaments and/or the anthers, forming a tube, anthers basifixed, introrse, 2-celled, cells opening lengthwise, 2 anterior anthers normally with a hairy tuft; disk absent, ovary (partly) inferior, 2-celled, style 1, hairy below the 2 stigmas, during anthesis lengthening through the anther tube, ovules numerous.
• Fruit a berry or an apically 2-valved capsule, crowned by the persistent calyx lobes; seeds numerous.
• Seed with straight embryo, albumen present.

Lobelia can be found flowering throughout the year, under humid conditions. Lobelia flowers are protandrous thus promoting outcrossing; by the lengthening of the style, the unopened stigmas grow through the anther tube, pushing the pollen out of the tube. The stigmas become receptive long after the pollen is shed.

Lobelia is sometimes classified into a family of its own, the Lobeliaceae, but this view is not shared here. The genus Pratia, with berry-like fruits, has been merged into Lobelia, with capsular, apically 2-valved fruits, because they are closely related, and an intermediate species exists, L. angulata, in which intergrading fruit types occur. Many Lobelia species show large intraspecific chromosomal variation, although diploidy seems to be predominant.

Lobelia in Malesia grows mainly in the per-humid hills, but some species occur in the lowland where the climate is seasonal.

Lobelia is propagated by seed, and some species also by stolons. L. chinensis is normally propagated vegetatively by stolons, which are dispersed by water.

Hairy roots of L. chinensis were induced with Agrobacterium rhizogenes ATCC 15834 in vitro, and produced 3 polyacetylene glycosides, lobetyol, lobetyolin and lobetyolinin, in hormone-free Murashige & Skoog, Gamborg B5, Woody Plant (WP) and Root Culture media. The hairy roots produced maximum amounts of the polyacetylenes, particularly in WP medium in the dark.

From ornamental Lobelia some fungal and bacterial diseases are known, caused by e.g. Alternaria tenuis, Coleosporium campanulae and Xanthomonas campestris, but these do not attack the medicinal Lobelia treated here. Lobelia is susceptible to nematodes.

In Vietnam, L. chinensis is harvested mainly during the rainy season, L. nicotianaefolia and L. angulata at the end of the rainy season.

In Vietnam, L. chinensis is used fresh or dried for future use. In India, L. nicotianaefolia is usually dried before use. The material is then studded with small spots of resinous exudation, which taste hot and acrid.

The Lobelia species treated here are rather widespread in Asia, but occur less in Malesia. As their preferable habitat is montane forest, there might be a risk of genetic erosion with the destruction of these habitats or through overexploitation.

There are no known breeding programmes of Lobelia.

L. nicotianaefolia, and probably other Lobelia species as well (e.g. L. chinensis), contain interesting alkaloids, similar to those of L. inflata. More research is needed to evaluate the composition of alkaloids and their quantity, as well as the optimal growing conditions of the species concerned. The potential for cultivating Lobelia, including L. inflata, in South-East Asia needs further investigation, since at present the use of the alkaloids mentioned is only very limited.

• Datta, A. & Datta, S.C., 1951. Pharmacognostic investigations on Lobelia pyramidalis Wall., a substitute for Lobelia inflata Linn. Journal of Scientific and Industrial Resources (India) 10B: 218–-283.
• Hewage, C.M., Bandara, B.M.R., Karunaratne, V., Wannigama, G.P., Pinto, M.R.M. & Wijesundara, D.S.A., 1998. Antibacterial activity of some medicinal plants of Sri Lanka. Journal of the National Science Council of Sri Lanka 26(1): 27-34.
• Moeliono, B. & Tuyn, P., 1960. Lobelia. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Series 1, Vol. 6. Wolters-Noordhoff Publishing, Groningen, the Netherlands. pp. 121–-136.
• Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing Co., Quezon City, the Philippines. pp. 952-–953.
• Subarnas, A., Tadano, T., Nakahata, N., Arai, Y., Kinemuchi, H., Oshima, Y., Kisara, K. & Ohizumi, Y., 1993. Pharmacological properties of beta-amyrin palmitate, a novel centrally acting compound, isolated from Lobelia inflata leaves. Journal of Pharmacy and Pharmacology 45(6): 545-550.
• Teng, L., Crooks, P.A. & Dwoskin, L.P., 1998. Lobeline displaces [3H]dihydrotetrabenazine binding and releases [3H]dopamine from rat striatal synaptic vessels: comparison with d-amphetamine. Journal of Neurochemistry 71(1): 258-–265.

• G.H. Schmelzer