Phytolacca (PROSEA)

Plant Resources of South-East Asia
Introduction

Protologue: Sp. pl. 1: 441 (1753); Gen. pl. ed. 5: 200 (1754).

Family: Phytolaccaceae

Chromosome number: x= 9; P. acinosa: n= 9, 2n= 36, 72, P. americana: n= 9, 2n= 36, P. dodecandra: 2n= 36, P. octandra: 2n= 36

Major species

Phytolacca acinosa Roxb.,
P. americana L.

Vernacular names

Pokeweed (En)
Vietnam: thương lục.

Origin and geographic distribution

Phytolacca consists of 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. No species occur naturally in South-East Asia, but a few have been introduced and these have sometimes naturalized.

Uses

In traditional medicine in Vietnam the roots of P. acinosa are considered to be diuretic and antiphlogistic, and are used internally (as a decoction) against dropsy, ascites, oedemas and pleuritis. Externally they are used against pharyngitis, boils and swellings. Outside South-East Asia the uses of roots of P. acinosa and P. americana (e.g. in Chinese medicine) are, in addition to those already mentioned, antiparasitic, laxative and antirheumatic, and against apoplexy, tumours and bronchitis.

Berries of the African P. dodecandra are a potent molluscicide, and can be used to control bilharzia-transmitting snails. They are also used as a soap substitute in Ethiopia. In Africa, parts of the plant are used for various medicinal purposes.

The young shoots and leaves of several Phytolacca species, when cooked, are used as a vegetable. After their toxic constituents have been removed, the red fruits of P. americana can be used to colour wine and foods. Some species, particularly P. americana, are common ornamentals in temperate climates. They are sometimes weeds.

Production and international trade

To date, Phytolacca has not been important as a medicinal plant in South-East Asia except in countries in Indo-China, where it is sometimes cultivated as a medicinal plant in pots or home gardens. Plant parts or products are not traded commercially.

Small areas of P. dodecandra are grown in Ethiopia, Swaziland, Zambia and Zimbabwe. Experimental trials for its introduction in Indonesia are being started.

Properties

Phytolacca leaves, fruits and roots contain numerous triterpenoids, e.g. phytolaccagenin, isophytolaccagenin, phytolaccagenic acid, isophytolaccinic acid, phytolaccanol, acetylaleuritolic acid, acinospesigenin, acinosolic acid, esculentic acid, esculentagenic acid, esculentagenin, jaligonic acid and spergulagenic acid.

On a dry weight basis the pericarp of P. dodecandra berries contains 25% bidesmosidic saponins with an oleanolic-acid aglycon; these saponins have molluscicidal properties. At concentrations well below 75 mg/kg, and after a certain period of exposure, fish and snails are killed. Other water animals such as insect larvae and tadpoles, are not affected at the concentrations that kill fish and snails. Tests showed that P. dodecandra berries have a potential use against Schistosoma larval stages in fresh water in schistosomiasis control programmes; they have cercariacidal and miracidiacidal properties.

Anti-inflammatory activity is attributed to the triterpenoid saponins, such as phytolaccoside and esculentoside, which are common e.g. in the roots. The inhibition of antibody production may partially explain the anti-inflammatory effect. Fungistatic properties have also been attributed to the saponins (e.g. yiamoloside from P. octandra ). The bark and the roots of several species (e.g. P. dodecandra) are poisonous for people and animals. The toxicity may manifest in hallucinations. Lethal poisoning of horses caused by Phytolacca roots has been reported. Patients using Chinese drugs containing Phytolacca have also been poisoned. Aerial parts of P. americana have been found to have antigalactagogic effects in cattle. The roots of P. acinosa and P. americana have hypotensive properties; they contain the hypotensive agents histamine and gamma-aminobutyric acid. When ingested, leaves of P. americana typically produce self-limited but severe gastro-enteritis, characterized by intense vomiting and frothy diarrhoea.

Tests with mice suggest that P. acinosa polysaccharides augment the immunological functions in vivo and inhibit tumour growth; the antitumour effect may be mainly related to the augmenting effect on macrophages in the mice. Leaf and seed extracts of several species have shown antiviral activity in tests, e.g. against golden mosaic virus and tobacco mosaic virus in beans and tobacco, and against sugar cane mosaic virus and cucumber green mottle mosaic virus, and also against viruses in animal cells. The complete amino acid sequence of antiviral protein from P. americana seeds has been determined. The proteins are ribosome-inactivating. The lectins from the roots of P. octandra are mitogenic for unseparated human peripheral blood lymphocytes and stimulate plasma cell formation. Lectins from the roots of P. americana are called pokeweed mitogen (PWM). They are haemagglutinating (tested with human blood group A erythrocytes) and mitogenic (determined by ³H-thymidine incorporation in lymphocyte cultures). Pokeweed mitogen plays an important role in fundamental leukocyte research.

The roots, leaves, and particularly, seeds of P. acinosa have abortifacient activity in mice. Extracts of P. americana have lysozyme activity. Fruits of P. acinosa and P. americana contain betalains such as humilixanthin. Lectins from P. americana have insecticidal properties. The neo-lignans americanol and isoamericanol from the seeds of the latter species showed neurotrophic properties in in vitro tests with rat cells. P. americana shows allelopathic activity: it may inhibit seed germination and seedling growth of crops like lettuce, sesame and cucumber.

The berries of P. americana contain the red betacyanin pigment phytolaccanin, which is identical to betanin from beetroot. The toxic saponins must be removed before this pigment is used as a food colourant. The colourant can be used in foods with a wide range of acidity, since it is not influenced by pH; however, its stability at room temperature is poor, so it is recommended for refrigerated and frozen foods.

The leaves of P. acinosa are reported to be a rich source of iron, phosphorus and calcium; fresh samples contain 84% water and 2.4% ash.

Adulterations and substitutes

In Japan, roots of Cynanchum caudatum Maxim. are used as a substitute for Phytolacca roots; they are also diuretic. Hibiscus sabdariffa L., Tamarindus indica L. and Tacca leontopetaloides (L.) O. Kuntze show toxic activity against snails transferring the parasitic trematode Schistosoma mansoni (causing bilharzia), which is comparable to Phytolacca dodecandra.

Description

Erect or scandent perennial herbs, sometimes shrubs and rarely trees, usually glabrous except for the often papillate or short-haired main axis of the inflorescence; stems up to 3 m long, but up to 10 m when scandent, often angular; roots often long and fleshy or tuberous.
Leaves alternate, simple and entire, usually ovate-oblong to oblong-lanceolate, herbaceous, acute at both ends, petiolate; stipules absent.
Inflorescence terminal or pseudolateral, racemose, often long, sometimes spiciform.
Flowers usually bisexual, but sometimes functionally male or female, actinomorphic, pedicel often short; perianth 5-partite, herbaceous, greenish, whitish or pinkish during anthesis and dark red under the ripe fruit, tepals free, equal or slightly unequal, ovate or obovate to lanceolate, persistent, spreading during anthesis, later often reflexed; stamens (6-)7-22(-33), in 1 or 2 series, inserted on the outer margin of the disk, sometimes also partly on the underside of the disk, filaments usually free, filiform-subulate, anthers dorsifixed, bilobed at both ends; carpels (3-)5-10(-16), whorled, laterally connate into a superior depressed-globose ovary, or almost free (P. acinosa and P. dodecandra), ovules solitary and basal in each carpel, styles terminal on the inner angle of the carpels, subulate, short, erect or recurved.
Fruit a depressed-globose berry, longitudinally 5-10-furrowed, or apocarp, juicy, orange or dark red to black, usually 5-10-seeded.
Seeds strongly laterally compressed, oval to lenticular, inaequilateral at base, shining black; embryo large, peripheric, enclosing the endosperm.

Growth and development

In Ethiopia P. dodecandra flowers and fruits throughout the year, but with a peak during the dry season. Plants in the shade often do not flower. Pollination is effected by insects such as ants, flies and spider wasps. Phytolacca fruits are often eaten by birds which disperse the seed. Sometimes monkeys also eat the fruits.

Other botanical information

Phytolacca belongs to the subfamily Phytolaccoideae, together with the genera Anisomeria and Ercilla, which are both restricted to South America.

Phytolacca species are often difficult to distinguish. Many of the morphological characters appear to be under weak genetic control. Moreover, many species hybridize readily, thus obscuring the characters by which they are recognized. Three highly molluscicidal and productive cultivars of P. dodecandra have been developed and are now in production in eastern and southern Africa.

Ecology

In South-East Asia, Phytolacca speces are found in open forest and forest borders, roadsides, along watercourses and in waste places, up to 1700 m altitude in Java. They occur very locally in South-East Asia, but are common in some locations. P. dodecandra usually occurs in Africa at altitudes above 1000 m, with an annual rainfall of about 1400 mm and a distinct dry period.

Propagation and planting

Mass multiplication is done by non-woody stem cuttings. It is advantageous to use a 50-75 mg/kg α-naphthalene acetic acid solution as root-promoting substance, and a slightly acid soil medium. After 6-8 weeks rooted cuttings can be planted in the field, usually at 1-3 m × 2-3 m. Propagation by seed is only appropriate for selection purposes. Soaking seed of P. americana in e.g. concentrated H₂SO₄ prior to sowing improves germination rate. Seed of P. dodecandra takes about 14 days to germinate.

In vitro production of active compounds

Betacyanins have been produced in cell cultures of P. americana initiated from stem explants. The cells were maintained in Schenk-Hildebrandt medium. The suspension was subcultured every week in darkness at 25°C, and calluses were subcultured every 3 weeks. Whereas in fruits prebetanin (betanin 6'-O-sulphate) and its isoform predominate, in the cell culture feruloylated derivatives occur as the major components. Callus cultures of P. americana can be stored at 4°C for at least 3 months, but betalain production of cultures that have been stored is inferior. A dual culture consisting of callus of P. americana and the fungus Botrytis fabae showed marked fungicidal activity to Cladosporium herbarum. The main active constituent of this extract was identified as phytolaccoside B.

Husbandry

Plantings of P. dodecandra must be shaded in the first weeks. Occasional watering and weeding are important until the crop has become established.

Diseases and pests

P. dodecandra plantings may be attacked by leaf and stem borers (Gitona spp.), so far the only serious insect pests. Precautions have to be taken against soilborne insect larvae.

Harvesting

The content of saponins of P. dodecandra berries varies seasonally: berries harvested during the dry season just before the onset of the rains have the highest content. Berries possess the highest molluscicidal potency when fully developed but still unripe. Complete fruiting racemes are collected and dried in the open under shade.

Yield

About 1000 kg dry fruits of P. dodecandra can be obtained per ha per year, i.e. about 250 g of dry fruits per plant annually.

Handling after harvest

Dry fruits of P. dodecandra can be stored for many years without losing molluscicidal activity. While grinding the berries care should be taken to avoid contact with the dust because it irritates the mucous membranes.

Genetic resources and breeding

Phytolacca occurs in South-East Asia only in cultivation or as an escape. The species highlighted here have a wide distribution and are rather commonly cultivated and naturalized outside South-East Asia. With the exception of P. dodecandra and some ornamentals (particularly P. americana) there has been no serious selection and breeding.

The world germplasm collection of P. dodecandra covers all the highland areas in Africa between 20°N and 30°S. There is abundant morphological variation. In Ethiopia, the Institute of Pathobiology in Addis Ababa has a collection.

Prospects

Although Phytolacca species are little known in South-East Asia, they might be promising for planting. The medicinal properties are interesting and comparatively well documented and, moreover, the plants also have molluscicidal, insecticidal and possibly fungicidal properties, and can be used as a vegetable and ornamental. Undoubtedly, several Phytolacca species are able to grow well in South-East Asia, particularly at higher elevations. However, more research is needed on planting requirements and uses, to realize the potential of these plant resources.

The use of P. dodecandra as a molluscicide might be limited, since the frequent applications required to ensure that treated waters remain clear of snails might also drastically reduce the fish population. However, as infected snails only occur at locations heavily frequented by people, berry suspensions can be applied locally. A few square metres of cultivated plants will enable people to treat their snail-infested watersides themselves, preferably during the dry season.

Literature

Bodger, M.P., McGiven, A.R. & Fitzgerald, P.H., 1979. Mitogenic proteins of pokeweed - part 1: purification, characterization and mitogenic activity of 2 proteins from pokeweed (Phytolacca octandra). Immunology 37(4): 785-792.
Fukuyama, Y., Hasegawa, T., Toda, M., Kodama, M. & Okazaki, H., 1992. Structures of americanol A and isoamericanol A having neurotrophic properties from the seeds of Phytolacca americana. Chemical and Pharmaceutical Bulletin 40(1): 252-254.
Hamilton, R.J., Shih, R.D. & Hoffman, R.S., 1995. Mobitz type I heart block after pokeweed ingestion. Veterinary and Human Toxicology 37(1): 66-67.
Kobayashi, A., Hagihara, K., Kajiyama, S., Kanzaki, H. & Kawazu, K., 1995. Antifungal compounds induced in the dual culture with Phytolacca americana callus and Botrytis fabae. Zeitschrift für Naturforschung, Section C, Biosciences 50(5-6): 398-402.
Lugt, Ch.B., 1989. Phytolacca dodecandra L'Hér. In: Westphal, E. & Jansen, P.C.M. (Editors): Plant Resources of South-East Asia. A selection. Pudoc, Wageningen, the Netherlands. pp. 224-225.
Nguyen Van Duong, 1993. Medicinal plants of Vietnam, Cambodia and Laos. Mekong Printing, Santa Ana, California, United States. 528 pp.
Nowicke, J.W., 1969. Palynotaxonomic study of the Phytolaccaceae. Annals of the Missouri Botanical Garden 55(3): 294-364.
Wang, H.B., Zheng, Q.Y., Qian, D.H., Fang, J. & Ju, D.W., 1993. Effects of Phytolacca acinosa polysaccharides I on immune function in mice. Acta Pharmacologica Sinica 14(3): 243-246.
Yeung, H.W., Feng, Z., Li, W.W., Cheung, W.K. & Ng, T.B., 1987. Abortifacient activity in leaves, roots and seeds of Phytolacca acinosa. Journal of Ethnopharmacology 21(1): 31-36.
Zhu, X. & Hu, Z., 1989. Preparation of the antiviral protein from pokeweed seeds and assay of its toxicity. Acta Botanica Yunnanica 11(4): 440-448.

Selection of species

Authors

Razali Yusuf