Calotropis (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Calotropis R.Br.

Protologue: Asclepiadeae 28 (1810); Mem. Wern. Nat. Hist. Soc. 1: 39 (1811).

Family: Asclepiadaceae

Chromosome number: x= 11; C. gigantea, C. procera: 2n= 22

Major species

• Calotropis gigantea (L.) Aiton f.,
• C. procera (Aiton) Aiton f.

Vernacular names

• Giant milkweed, swallow wort (En).
• Arbre à soie (Fr).

Origin and geographic distribution

Calotropis is a small genus of 3 species, distributed throughout the Old World tropics. Two species occur from tropical Africa to Malesia, the third, C. acia F. Ham., is restricted to India, Bangladesh and Nepal. Both C. gigantea and C. procera are now pantropical, initially cultivated but often escaped, particularly in arid locations.

Uses

Calotropis species generally have similar uses. Many uses originate from India, and have spread to Africa, South-East Asia and South America. The whole plant is used for skin diseases, boils and sores and as a tonic and purgative in small doses, and as an emetic in larger doses. The powdered root bark is used to cure dysentery, elephantiasis, and leprosy. The stem bark is diaphoretic and expectorant, and is used for dysentery, spleen complaints, convulsions, osteomyelitis, lumbago, scabies, ringworm, pneumonia, and protracted labour. The latex is used on stings, toothache, caries, ringworm, leprosy, syphilis, rheumatism and tumours, and also as an antiseptic, vermifuge, emetic and purgative, as well as for poisoning arrows. The powdered flowers are given for coughs, colds and asthma. The leaves are applied on burns, headaches and rheumatic pains, and as a tincture for intermittent fever. In Vietnam, leaves are taken as a cardiotonic, and a decoction of leaves is used in asthma, with a delayed effect of 2-3 days, or sometimes up to 7-8 days. Secondary effects are tiredness, diarrhoea and vomiting. In Ambon, treatments for snake bites include chewing the root of C. gigantea, swallowing the juice, and applying the mashed root to the bite. In Java, the powdered roots mixed with rice are rubbed on tired feet, and the smoke from burning leaves is inhaled for catarrh. In Thailand, the flowers are applied to skin diseases. In Curaçao and the Bahamas, the fresh leaves of C. procera are bound to the head to relieve headache, and to the feet for sprains and swellings. Crushed leaves are heated and smeared on rheumatic or stiff limbs.

In the past both C. gigantea (Madar fibre) and C. procera (French cotton or Akund) were cultivated and used as a source of a strong fibre, and their seed floss was used for packing, as it was too short and too light for spinning. They have also been tested for use in the paper pulp fabrication, and as a source of methane, through anaerobic fermentation. Calotropis species are not often used as fuel wood, as they are of poor quality. In Indo-China, charcoal from the wood was used in gun powder and fireworks. Calotropis produces many leaves, which can be used for mulching, green manuring of rice fields and for binding sandy soil. In Vietnam, C. gigantea is planted as a hedge plant. In Africa, the wood is also used as a toothbrush. The gynostegium is used by the Chinese in Indonesia in sweetmeats. In the Philippines, C. gigantea is not medicinally used, but the flowers are strung into rosaries. In Thailand, the flowers are used in wedding ceremonies, due to the name "rak", which means love.

Production and international trade

Calotropis is not traded internationally in South-East Asia but is readily available for local use, as it is commonly grown in the villages. The leaves are widely sold in local markets.

Properties

All parts of C. gigantea are toxic, due to the presence of several cardiac glycosides (cardenolides). The latex contains the cardenolides calotropin, calotoxin and uscharin (which has been patented), as well as the proteolytic enzyme calotropain. The cardiac glycosides calotroposide A and B have been identified in the root bark, together with the resinolsβ-calotropeol and giganteol. Giganteol, α- and β-calotropeol were also isolated from the stem, as well as β-calotropeol from the flowers. In addition, the leaves contain the cardenolides calotropine and gigantine, and the roots calotropine, frugoside and 4'-O-β-D-glucopyranosylfrugoside.

Cardiac glycosides are also the toxic components of C. procera. The latex contains cardenolides such as calotropin, calotroposide, calactin, calotoxin, uscharin, uscharidin, voruscharin and proceroside, and the proteolytic enzyme calotropain. The plant also contains the aglycone proceragenin, which has antibacterial properties.

Calotropin is a quick acting heart stimulant, and is known to be 15-20 times more poisonous than strychnine: minute amounts can cause death. In the cat, the cardiotonic actions of calotroposide, calotoxoside and uscharin are 83%, 76% and 58% of the action of ouabain, respectively. The lethal dose for calotropin is 0.12 mg/kg. In addition to cardiac glycosides, several triterpenes, cyclosadol, cycloart-23-ene-3β-25-diol, α-lactucerol and lupeol have been isolated.

Most phytochemical tests have been done with C. procera. Aqueous and alcoholic extracts of the root of C. procera initially produce a light depression, followed by a stimulation of the rate and force of myocardial contractions in isolated frog and rabbit hearts. They also produce marked vasoconstriction in frog and rat and a persistent rise in blood pressure in dog, which cannot be altered by sympathetic drugs. In goats, latex administered orally at doses of 1 ml/kg, or 0.005 ml/kg intravenously or intraperitoneally, caused death between 4 minutes and 4 days. The small doses given orally or intramuscularly, caused no death. Main features in the goats were nervous signs, frequent urination, frothing at the mouth, dyspnoea and diarrhoea. Lameness was observed in goats given latex via the intramuscular route. At the site of the injection haemorrhagic myositis occurred, and in general, haemorrhages, pulmonary cyanosis, enterohepatonephropathy and peritonitis were observed, as well as increased concentrations of cholesterol, urea and creatinine, and a decrease in the level of general protein. The toxicity of the latex was also tested in the black rat (Rattus rattus), which was fed bait, with a latex concentration of 5, 7.5 or 10% for a period of up to 10 days. It produced sedation, dyspnoea, weakness, weight reduction, anorexia, diarrhoea, bleeding from nose, eyes and anus, mild tetanic convulsions, collapse and death. The latex of both Calotropis species exhibits uterine stimulation in albino rats which may result in abortion.

Some literature reported that, in the case of Calotropis poisoning, demulcent and mucilaginous drinks like milk or rice-gruel should be given, and morphine and atropine administered to relieve pain. Calotropis is also known to cause allergic contact dermatitis, and the latex causes kerato-conjunctivitis.

Further pharmacological activities of C. procera extracts includesignificant anti-ulcer activity against aspirin, indomethacin, ethanol, indomethacin + ethanol, or stress-induced ulcerations in rats, by the chloroform fraction of the root extract. Significant inhibition of gastric secretory volume and total acidity in pylorus ligated rats was also observed, as well as inhibition of the arachidonic acid metabolism induced by soya bean lipoxygenase, suggesting that the anti-ulcer activity might be attributable to the inhibition of 5-lipoxygenase.

An aqueous suspension of the dried latex was significantly effective as an anti-inflammatory in a carrageenin- and formalin-induced rat paw oedema model, as was the chloroform-soluble fraction from the roots in rats using the models of carrageenin-induced pedal oedema, cotton pellet granuloma and formaldehyde-induced arthritis. In addition, a significant analgesic potential was demonstrated using acetic acid-induced writhing in mice. The ethanol extract of the aerial parts was also tested in guinea-pig for its antipyretic, analgesic, anti-inflammatory, antibacterial, purgative and muscle relaxant activities, and showed significant antipyretic, analgesic and neuromuscular blocking activity. However, no significant anti-inflammatory or antibacterial activity was shown. Furthermore, an aqueous extract of the leaves and stem bark had significant cough-suppressing activities upon bronchial irritation by ammoniac in guinea-pigs, and a chloroform extract of the chloroform-soluble fraction from the roots caused a significant reduction in experimentally induced acute and chronic liver injury by carbon tetrachloride in rats. The alcoholic extract of the leaves of both C. procera and C. gigantea exhibited anticancer activity against human epidermal carcinoma of the nasopharynx in tissue culture, as did an ethanol extract of C. procera flowers on cultivated tumour-cells. Finally, the enzyme calotropain is said to be more active than papain, bromalein or ficin.

An extract of the leaves applied on rice had a marked molluscicidal activity against the golden apple snail in the Philippines, as well as against other snails elsewhere; this is caused by uscharin. The petroleum ether and acetone extract of the aerial parts show a marked effect on the mortality of late 3rd instar larvae of the mosquito Culex quinquefasciatus, and also in last instar larvae of the groundnut pest Spodoptera litura. The ethanol extract of the leaves shows the highest toxicity of all solvents used, against all life stages of the flesh fly (Sarcophaga haemorrhoidalis). The powder of the leaves showed mortality of the bruchid Callosobruchus chinensis feeding on stored seeds of cowpea (Vigna unguiculata (L.) Walp.), although the damage to the seeds was 7.6%, compared to malathion at 2.2%. The leaf extract showed high antifeedant activity against 3rd instar larvae of the teak skeletonizer (Eutectona machaeralis).

Several extracts of the leaves revealed strong antimicrobial activity in vitro against Clostridium perfringens, Klebsiella ozaenae, Pseudomonas aeruginosa, Salmonella typhi and Streptococcus faecalis, as well as other species. The latex showed similar activity against Candida albicans , Escherichia coli, Klebsiella pneumoniae, Proteus vulgaris, Pseudomonas aeruginosa, Salmonella gallinarum and Staphylococcus aureus. The ethanolic extract of the flowers significantly inhibited the growth of both gram-positive and gram-negative bacteria.

The latex, the aqueous or ethanol extract of the flowers or leaves, or chopped plant parts mixed in the soil, show strong nematicidal effects against Helicotylenchus dihystera, Meloidogyne spp., Tylenchorhynchus brassicae and other nematodes, as well as their egg masses. The latex inhibited activity in vitro and inhibited infection of tobacco mosaic virus, when sprayed on the leaf surface of tobacco before and after inoculation. It also inhibited 2 strains of watermelon mosaic virus. Apart from plant viruses, the leaf extract is also active against the herpes simplex type-1 and vesicular stomatitis viruses in humans. The leaf extract and latex are also active in vitro against several plant pathogens, including Alternaria brassicicola, Colletotrichum capsici, Fusarium oxysporum, Rhizoctonia solani and Sclerotinia sclerotiorum.

Adulterations and substitutes

In Asia C. gigantea is used as a substitute for ipecacuanha (Psychotria ipecacuanha (Brot.) Stokes), from tropical America, as an effective cure for amoebic dysentery, but it has a stronger tendency to produce vomiting and depression. In Africa, lemon juice is sometimes used as a substitute for the latex of C. procera as a coagulant for making soft white cheese.

Description

• Erect, much-branched shrubs or small trees with abundant milky latex, covered with woolly hairs when young.
• Leaves opposite, thick, fleshy and broad, underneath with woolly tomentum, glands at leaf basis; petiole absent or short; stipules absent.
• Inflorescence composed of many-flowered, erect, axillary umbellate cymes, 1 per axil; peduncle present; pedicel present.
• Flowers 5-merous; calyx 5-lobed with many glands at the base on the inside; corolla broadly campanulate, deeply divided into 5 lobes, fleshy; staminal corona of gynostegium with 5 fleshy lobes enlarged at base into an upturned horn and auricles, stamens with filaments joined in a tube, anthers short, pollinia 5, pollinium sacs 2, united by 2 pendulous translator arms 2 mm long; stigma head flattened, 5-lobed.
• Fruit an aggregate of 2 dry follicles, each ovoid-oblong, curved on the outside, with a very oblique base and pointed tip, fleshy.
• Seeds many, flattened, ovoid, with an apical tuft of white silky hairs (coma), 2-3 cm long.
• Seedling with epigeal germination.

Growth and development

Calotropis is fast growing, and flowers throughout the year, but especially during the hot season. It is primarily pollinated by bees, butterflies and wasps.

Other botanical information

Calotropis belongs to the tribe Asclepiadeae of the subfamily Asclepiadoideae, and was known to contain 6 species, 3 of which are now considered a synonym of C. procera. The tribe is characterized by anthers with membranaceous tips and pollinaria with pendulous pollinia. Genetic variation is expressed in white-flowered forms of C. gigantea, and larger leaves of African C. procera plants than those from Asia.

Ecology

Calotropis grows especially on littoral sandy soils and dry uncultivated land, with periodic dry periods.

Propagation and planting

Calotropis can be grown from seed or stem cuttings. The seeds are spread by wind and water. Callus cultures of C. procera on Murashige and Skoog medium showed a marked increase in laticifer differentiation (10-30%) with increasing age of the cultures or when supplied with 1% of its own latex, or with the auxin indole acetic acid (IAA).

Husbandry

In Thailand, a trial on plant spacing of C. gigantea for medicinal purposes showed that a spacing of 0.5 m × 0.5 m gave higher plants, whereas at 2 m × 2 m plants were wider, although the number of main branches did not differ significantly.

Diseases and pests

The leaf hopper Poecilocerus pictus (Orthoptera) is a pest of Calotropis plants. The oleander aphid (Aphis nerii) and the caterpillars of the tiger butterfly (Danaus chrysippus) feed on Calotropis, using the cardenolides as a chemical defence mechanism. The nematodes Meloidogyne incognita and M. javanica are found on the roots of Calotropis in India, although the leaf extract kills them.

Harvesting

The leaves of Calotropis are harvested throughout the year.

Yield

At a spacing of 0.5 m × 0.5 m, C. gigantea reaches a maximum height of 166 cm in 1 year, producing 7.3 t fresh leaves (1.1 t dry leaves) and 56 kg latex per hectare.

Handling after harvest

The leaves of Calotropis are cleaned with a cloth to remove the hairs, before being used fresh or dried in the sun.

Genetic resources and breeding

The ease of growing Calotropis and its widespread occurrence in villages, in sandy areas and on seashores means that it is in no danger of genetic erosion. Small germplasm collections of C. procera exist in Wakehurst Place in the United Kingdom and in Maracay in Venezuela.

Prospects

Calotropis species are considered very poisonous, due to the presence of cardiac glycosides. This toxicity will strongly limit its potential use in local medicine. Also, the patenting of the cardenolide uscharine has not led to its use as a medicine. Extracts of Calotropis species, however, display a range of interesting pharmacological activities, e.g. anti-ulcer and anti-inflammatory, which merit further research. In Thailand, the flowers of C. gigantea have economic potential as ornamentals used in ceremonies.

Literature

• Basu, A., Sen, T., Ray, R.N. & Chaudhuri, A.K., 1992. Hepatoprotective effects of Calotropis procera root extract on experimental liver damage in animals. Fitoterapia 63(6): 507-514.
• El Badwi, Samia, M.A., Adam, S.E., Shigidi, M.T. & Hapke, H.J., 1998. Studies on laticiferous plants: toxic effects in goats of Calotropis procera latex given by different routes of administration. Deutsche Tierarztliche Wochenschrift 105(11): 425-427.
• Mann, A., Abalaka, M.E. & Garba, S.A., 1997. The antimicrobial activity of the leaf extracts of Calotropis procera. Biomedical Letters 55(219): 205-210.
• Mossa, J.S., Tariq, M., Mohsin, A., Ageel, A.M., al-Yahya, M.A., al-Said, M.S. & Rafatullah, S., 1991. Pharmacological studies on aerial parts of Calotropis procera. American Journal of Chinese Medicine 19(3-4): 223-231.
• Neraliya, S. & Srivastava, U.S., 1996. Effect of plant extracts on post-embryonic development of the mosquito Culex quinquefasciatus. Journal of Advanced Zoology 17(1): 54-58.
• Rahman, M.A. & Wilcock, C.C., 1991. A taxonomic revision of Calotropis (Asclepiadaceae). Nordic Journal of Botany 11(3): 301-308.

Selection of species

• Calotropis gigantea
• Calotropis procera

Authors

• R. Kiew