Asclepias curassavica (PROSEA)
- Protologue: Sp. pl. 1: 215 (1753).
- Family: Asclepiadaceae
- Chromosome number: 2n= 22
- Swallow wort, red milkweed (En), blood-flower (India). Asclepias de Curaçao (Fr)
- Malaysia: bunga mas
- Philippines: bulak damo, kapul-kapul (Tagalog), anibung (Bontok)
- Laos: mak kha kay
- Thailand: fai duean haa (northern), thian daeng (central), mai cheen (south-western)
- Vietnam: bông tai, ngô thị.
Origin and geographic distribution
A. curassavica originates from South America and has now spread throughout the tropics and subtropics. In some locations it is now naturalized and has become a weed.
Entire plants are considered extremely poisonous and are not generally used. In South America, Burma (Myanmar), China, Indo-China and the Philippines, but not in other parts of Malesia, a decoction of the powder from the roots is used as an emetic and purgative, and also as an astringent for dysentery. The leaf juice taken as a syrup is mentioned as a vermifuge and a sudorific. The pounded fresh or dry leaves and flowers are applied as a dressing for wounds and sores, and a decoction of the flowers is styptic. The flowers are considered more potent than the leaves. In Peninsular Malaysia, the flowers are crushed in cold water and used as a poultice for headache. In Thailand, roots, leaves or the whole plants are applied on abscesses and wounds. In South America, fresh or dried and powdered leaves are applied on cancerous sores, and are used in the treatment of dysentery, piles and gonorrhoea. In Mexico, it is used internally in to treat cancer of the stomach, intestines, uterus and kidneys, and externally on malignant tumours. In Brazil, an infusion of the roots, with a little sugar, is used against blennorrhagia and leucorrhoea. The latex is placed in carious teeth as an anodyne. It is also used as a remedy for bites of poisonous animals and for warts. The latex is considered cicatrizant in Madagascar.
The follicles of Asclepias species contain a soft, fine floss, which is not of much value on account of its elasticity. It can however be used to stuff pillows. The fine bast fibre of A. curassavica may be applied in textiles in combination with cotton. It is also grown as an ornamental.
A. curassavica is suspected of cattle-poisoning, although cattle tend to avoid the plant, even when hungry and on overgrazed pastures during the dry season. Honey obtained from the plant is bitter, dark and thick.
Production and international trade
A. curassavica does not enter into international trade in Malesia, but bundles of the plant are sold in tropical American herb markets.
The toxic principle of A. curassavica is a mixture of cardiac glycosides, of which the latex contains at least 50%. These cardiac glycosides are of the cardenolide type, and in a very small dose cause frogs to die in half an hour, the ventricles being arrested in systole. One of the isolated glycosides, asclepiadin, is extremely poisonous, causing paralysis of heart muscles and death, but in a dry state it decomposes fast into an inert component and a sugar. Its pharmacological effects after application include salivation, nausea, vomiting, diarrhoea, paralysis of the muscles, cramps, and death if the paralysis extends to the heart. Another cardenolide, asclepin, isolated from the aerial parts, also showed a marked positive inotopic effect in vitro on the isolated atrium and heart preparations of guinea-pigs, and in vivo on the anaesthetized cat. It was found to be more active than g-strophanthin, digoxin, digitoxin or digitoxigenin.
Other cardiac glycosides isolated from A. curassavica include 3'-epi-19-norafroside and 12β-hydroxycoroglaucigenin from the shoots, and curassavicin, calotroposide and vincetoxin from the roots. The latex is reported to inhibit the growth of Candida albicans by causing deformation of the fungal cell wall.
Adulterations and substitutes
In the West Indies A. curassavica is used as a substitute for ipecacuanha ( Psychotria ipecacuanha (Brot.) Stokes). It is considered a more potent emetic, but has considerable side effects.
An annual to perennial, erect herb, 40-150(-250) cm tall, usually unbranched but sometimes with several branches, woody at base, young stems hairy, latex copious, white. Leaves opposite, narrowly lanceolate, 6-15 cm × 1-3 cm, base and apex acute, lateral veins conspicuous, 10-15 pairs, slightly pubescent beneath; petiole 3-20 mm long; stipules absent. Inflorescence an axillary umbel, mostly solitary, sometimes several together on a common peduncle 3.5-6 cm long, 4-15-flowered. Flowers actinomorphic, 5-merous, pedicel 12-25 mm long, erect, accrescent in fruit, pubescent; calyx lobes lanceolate, 2-3 mm long, with 5-10 minute basal glands inside, reflexed at anthesis, green; corolla with short tube and 5 expanded or reflexed lanceolate lobes, 7-9 mm × 3.5-4.5 mm, red, rarely yellow or white; gynostegium composed of a staminal column 2-4 mm long, topped with 5 erect, hood-like, fleshy lobes (corona), 3.5-4 mm × 1.5 mm, golden yellow to orange, bearing inside at the base a slender incurved hornlike appendage and many nectar cells, anthers with an apical incurved membrane, pollinia 5, pollinium sacs 2, compressed, yellowish, united by 2 pendulous translator arms, connected by a slitted gland, dark brown; ovary superior, pistils 2, stigma head flattened, 5-lobed. Fruit an aggregate of 2 dry follicles, each follicle fusiform, 5-8 cm × 0.8-1.5 cm, dehiscing along its ventral suture. Seeds numerous, broadly oval, flattened with a narrow wing, 5 mm long, with an apical tuft of silky hairs (coma), 2-3 cm long, white. Seedling with epigeal germination.
Growth and development
In climates without a dry season, A. curassavica flowers throughout the year. Asclepias species are entomophilous, and pollination occurs exclusively through insects, especially wasps and bees, but also butterflies, which are attracted by the abundant nectar. The pollinia stick with the gland to the legs of the insects which are trapped in the narrow slit of the pollinium gland. When visiting other flowers of the same species, the burdened leg slips into the stigmatic chamber where the pollinium sac breaks from the translator arm. When hand-pollinated A. curassavica appears to be completely self-compatible.
In North and Central America, the monarch butterfly ( Danaus plexippus ) oviposits preferably on milkweed plants, because these produce oviposition stimulants, flavonol glycosides. Caterpillars of the monarch butterfly, as well as lygaeid bugs ( Oncopeltus cingulifer and Lygaeus reclivatus ) of Costa Rica and the oleander aphid ( Aphis nerii ) use cardenolides from A. curassavica as a chemical defence mechanism. They obtain these by eating the leaves.
Other botanical information
Asclepias is a large genus, consisting of nearly 100 species of herbaceous plants. It has a mostly American distribution with a few African and West Indian representatives. There are no indigenous species in South-East Asia.
A. curassavica grows in sunny or slightly shaded habitats from sea-level up to 2400 m altitude, and has become naturalized in grassy and sandy areas, waste places, and coconut plantations, often in patches.
Propagation and planting
A. curassavica propagates by seed.
In vitro production of active compounds
Chromosome number and cardenolide production in A. curassavica plantlets grown in vitro from shoot tips and excised nodes were affected by the type and concentration of hormone used. Murashige and Skoog medium supplemented with kinetin + naphthalene acetic acid (NAA), kinetin + 2,4-D and indole acetic acid (IAA) produced cells with 2n = 33, 20 and 18 respectively, while the percentage of cardenolides ranged from 1.2-1.5, 1.5-2.3 and 1.6-2.8, respectively, after 60 days.
Diseases and pests
In Ecuador, leaf yellowing and premature death of A. curassavica is caused by a mixed infection of the flagellate protozoa Phytomonas sp. and Rhabdovirus-like particles. Phytomonas sp. causes the serious Cedros wilt disease of coconut in South America. Caterpillars of the monarch butterfly and related species, as well as the oleander aphid and some other larvae of cardenolide-tolerant species feed specifically on A. curassavica plants.
Plants of A. curassavica are harvested whenever the need arises.
Genetic resources and breeding
A. curassavica is an exotic plant that is widely grown as an ornamental, and there is no danger of genetic erosion. No germplasm collections or breeding programmes are known to exist.
A. curassavica is considered extremely poisonous, due to the presence of toxic cardiac glycosides, which in in vivo experiments have shown to be more potent than well known cardenolides used in therapy, e.g. strophanthin and digoxin. Its toxicity will therefore strongly inhibit the use of the plant in medicine.
- Dasgupta, M., Pramanik, T.K. & Datta, S.K., 1987. Mass propagation and genetic variability of two cardenolide plants in vitro. Acta Horticulturae 208: 263-271.
- Morton, J.F., 1981. Atlas of medicinal plants of Middle America. Bahamas to Yucatan. Charles C. Thomas, Springfield, Illinois, United States. pp. 687-688.
- Moulin-Traffort, J., Giordani, R. & Regli, P., 1990. Antifungal action of latex saps from Lactuca sativa L. and Asclepias curassavica L. Mycoses 33(7-8): 383-392.
- Patnaik, G.K. & Kohler, E., 1978. Pharmacological investigation on asclepin - a new cardenolide from Asclepias curassavica. Part II. Comparative studies on the inotropic and toxic effects of asclepin, g-strophantin, digoxin and digitoxin. Arzneimittelforschung 28(8): 1368-1372.
- Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing Co., Quezon City, the Philippines. pp. 742-744.
- Woodson, R.E., 1954. The North American species of Asclepias L. Annals of the Missouri Botanical Garden 41(1): 1-211.
Other selected sources
- Burkill, I.H., 1966. A dictionary of the economic products of the Malay Peninsula. Revised reprint. 2 volumes. Ministry of Agriculture and Co-operatives, Kuala Lumpur, Malaysia. Vol. 1 (A-H) pp. 1-1240, Vol. 2 (I-Z) pp. 1241-2444.
371, 389, 642, 786.