Phytolacca americana (PROTA)
|Geographic coverage Africa|
|Geographic coverage World|
|Dye / tannin|
|Forage / feed|
- Protologue: Sp. pl. 1: 441 (1753).
- Family: Phytolaccaceae
- Chromosome number: 2n = 36
- Phytolacca decandra L. (1763).
- Pokeweed, poke, inkberry, common pokeberry, red ink plant, poke root (En).
- Phytolaque, raisin d’Amérique, teinturier (Fr).
- Capa rosa, tintureira, uva de América, uva de macaco (Po).
Origin and geographic distribution
Phytolacca americana originates from southern and eastern North America and Mexico and has been introduced into South America, Europe, Africa and Asia. In Africa its occurrence is documented in Cape Verde, Liberia, DR Congo, Réunion, Mauritius, South Africa and Swaziland. It has probably been introduced into other countries of tropical Africa as well, but documentation is lacking.
In Réunion and Mauritius the powdered roots are applied to haemorrhoids. The crushed roots in alcohol are externally applied to rheumatic pains. The fruits and aerial parts have emetic and intestinal worm-expelling properties. In South Africa the root extract is taken to treat lung diseases. All plant parts, but especially the roots, are poisonous when taken fresh and in quantity. Symptoms of poisoning are burning of mouth and throat, salivation, severe stomach irritation, vomiting, bloody diarrhoea, spasms and convulsions; death may result from ingestion.
In the United States and Europe different plant parts are widely used to treat haemorrhoids, rheumatism, inflammations, skin diseases including skin parasites and cancer, general pain (fruit, roots), swellings, wounds and ulcers (leaves). The root extract is taken as an abortifacient and to treat sore throat and tonsillitis. The powdered roots are applied in a poultice to treat cancer. The fruit and seed extract is taken as a purgative, emetic, and to treat venereal diseases, scurvy and snakebites.
In Cape Verde the fruits are used as food colorant, but the toxic substances must be removed first. In the United States and Europe the fruits have been used in traditional textile dyeing. They provide the red pigment ‘Phytolacca red’, but fruits are not permitted as a food dye, e.g. in Germany. The fruits were formerly used to reinforce the red colour of wine. In Réunion and Mauritius the young shoots are thoroughly cooked and eaten as a vegetable. This use is also widespread in the United States. Phytolacca americana is planted as an ornamental in temperate climates.
Production and international trade
Although much research is currently being done on different compounds of Phytolacca americana, no quantitative information is available on production and trade of these compounds. In human and veterinary herbal medicine the root tincture is sold as an emetic.
The leaves, fruits and roots contain several saponins (triterpenoid glycosides), i.e. phytolaccosides and esculentosides, with phytolaccosides B, E and G as main compounds. The anti-inflammatory activity of the roots has been attributed to the phytolaccosides and esculentosides. Phytolaccosides cause haemolysis of red blood cells. Phytolaccoside B prevents genetic modification of plants via Agrobacterium tumefaciens. It acts as a genuine plant transformation inhibitor, having neither anti-agrobacterial nor phytotoxic activity.
The roots, fruits and leaves contain several lectins, mitogenic-acting cysteine-rich glycoproteines, also known as pokeweed mitogens (PWMs) and pokeweed antiviral proteins (PAPs). The mitogens have a stimulating effect on the immune system, especially on the proliferation of T- and B-lymphocytes, and play an important role in fundamental leukocyte research. For several decades, PWMs have been investigated as a therapeutic agent for cancer treatment in animal models. PAPs represent a group of ribosome-inactivating proteins (RIPs). They are N-glycosidases that catalytically remove a specific adenine residue from ribosomal RNA. They not only inactivate both eukaryotic and prokaryotic protein synthesis, but also inhibit the mechanical transmission of viruses. They have potent antiviral activity against many plant and animal viruses, including T-cell leukaemia virus, lymphoma virus, as well as human immunodeficiency viruses. PAPs show unique clinical potential to become the active ingredient of an antivirus drug because of their potent in-vivo anti-HIV activity and non-interference with in-vivo sperm functions. Some PAPs (PAFPs) also exhibit a broad spectrum of antifungal activity, including inhibition of certain saprophytic fungi and some plant pathogens.
The saponins and lectins are responsible for the toxicity of the plant, especially of the roots and seeds. Lethal poisoning of horses caused by eating the roots has been reported. The roots also have hypotensive properties; they contain the hypotensive compounds histamine and γ -aminobutyric acid. When ingested, leaves typically produce severe gastro-enteritis, characterized by intense vomiting and frothy diarrhoea. Aerial parts have been found to have antigalactagogic effects in cattle. Toxicity tests from extracts of the roots and fruits showed that only ripe fruits have significant molluscicidal properties, and are not toxic to other organisms at recommended doses. The methanol extract of dried seeds contains several antihepatotoxic neolignans, of which americanin A showed significant anti-inflammatory activity with very weak toxicity in tests with rats. α-Spinasterol has been isolated from the chloroform extract of the roots, shows anti-inflammatory properties, acts as an antimutagen and has therapeutic potential to modulate the development and progression of diabetic nephropathy.
The fruits contain the red pigment phytolaccanin, which is identical to betanine, commercially extracted from beetroot (Beta vulgaris L.).
Several phytolaccosides have been isolated from callus mass derived from the stems and roots.
Climbing or scrambling, semi-succulent, reddish herb up to 3.5 m tall, glabrous, with a fleshy taproot becoming very large. Leaves alternate, simple and entire; stipules absent; petiole 2–6 cm long; blade lanceolate to elliptical or ovate, 14–22 cm × 6–12 cm, base rounded, often asymmetrical, apex acute. Inflorescence an erect, axillary raceme up to 30 cm long, many-flowered; bracts up to 3 mm long, lanceolate. Flowers bisexual, regular, 5-merous, sweet-scented; pedicel up to 12 mm long, pink; sepals c. 2 mm long, rounded, whitish to pinkish; petals absent; stamens c. 10, free, filaments c. 2 mm long; ovary superior, consisting of c. 10 carpels, united or with free apices, styles connected, c. 1 mm long, stigmas linear. Fruit consisting of fused 1-seeded berries, smooth or sometimes ribbed, up to 6–8(–10) mm in diameter, ripening purplish black. Seeds kidney-shaped, laterally flattened, 3–4 mm long.
Other botanical information
Phytolacca comprises about 25 species, most of which are native to the tropical and subtropical regions of South and Central America, with a few species in Africa, Madagascar and Asia. Other Phytolacca species with united carpels are Phytolacca octandra L. (inkberry, dyeberry) and Phytolacca dioica L. (belhambra tree, pokeberry tree), both originating from South America and now pantropical.
In Africa Phytolacca octandra occurs in Nigeria, Kenya, Zimbabwe, Mozambique and South Africa. In South Africa the leaves are applied to septic wounds. A root maceration is drunk to treat lung ailments. Pulverized roots are taken as an emetic and applied externally to treat snakebites. Young sprouts and leaves can be used as a vegetable. The roots contain triterpenoid saponins and lectins.
Phytolacca dioica has been introduced in the drier regions of tropical Africa, and occurs in Cape Verde, Mali, Namibia, Botswana, Zimbabwe and South Africa. The leaves are eaten as a purgative. The fruit is poisonous. It is grown as an ornamental, roadside and shade tree. The leaves and seeds contain several ribosome-inactivating proteins (RIPs). The leaves are used in dying wool.
Growth and development
Phytolacca americana has a lifespan of 3–10 years. It flowers in spring or at the beginning of the rainy season. Fruits develop 2–3 months later. Fruit set is usually high, suggesting a high degree of selfing. In North America the relative density of the plants in a population increases with decreasing soil pH and decreasing content of available phosphate. The seeds are dispersed by birds.
Phytolacca americana occurs in sunny anthropogenic localities, such as disturbed forest, forest margins, roadsides, river banks, fallow land and waste places at low altitudes. It prefers humus-rich and acidic soil in well-drained to moist habitats. It tolerates short periods of drought.
Propagation and planting
Phytolacca americana is propagated by seed or stem cuttings. Prior to sowing, the fruits should be soaked in water for 48 hours to permit seed extraction. The seeds are sown in pots with humus-rich soil and regularly watered. Germination of unstratified seeds is generally high (about 80%), but may vary greatly both within as well as between plants. After one year, the seedlings can be transplanted into the field or in larger pots.
Mass multiplication is done by non-woody stem cuttings. It is advantageous to dip the end of the cutting in rooting powder or a rooting solution, plant in a slightly acid soil medium and to water regularly. After 6–8 weeks rooted cuttings can be planted in the field, usually at a spacing of 1–3 m × 2–3 m.
Regular watering and weeding are important until the crop is established.
Diseases and pests
In Africa diseases and pests have not been reported for Phytolacca americana. However, it is an alternative host to a number of viral diseases, including mosaic, ringspot and yellow viruses that affect Amaryllidaceae, Liliaceae and Solanaceae. In Italy wilt and die-back symptoms were observed on plants cultivated for ornamental purposes caused by Phytophthora nicotianae.
Very young, green leaves and sprouts are harvested in early spring for use as a vegetable. Roots are harvested at the end of the fruiting season.
Handling after harvest
The harvested plant parts are usually used fresh.
Phytolacca americana is a common herb in its natural distribution area and therefore not threatened by genetic erosion. A number of ornamental cultivars of Phytolacca americana have been selected for their larger infructescences.
Phytolacca americana has an interesting chemistry as it contains glycoproteins and molluscicidal saponins. The first category includes compounds that have a stimulating effect on the immune system, play an important role in fundamental leukocyte research, and have potent antiviral activity, offering possibilities for future antiviral medicine development. Phytolacca americana is also an attractive ornamental plant.
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Sources of illustration
- Walter, H., 1909. Phytolaccaceae. In: Engler, A. (Editor). Das Pflanzenreich. Regni vegetabilis conspectus. Volume 4 (83). Verlag von Wilhelm Engelmann, Leipzig, Germany. 154 pp.
- G. Aweke, P.O. Box 4278, Addis Ababa, Ethiopia
Correct citation of this article
Aweke, G., 2007. Phytolacca americana L. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 12 April 2021.
- See the Prota4U database.