Polygala (PROSEA)
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Introduction |
Polygala L.
- Protologue: Sp. pl. 2: 701 (1753); Gen. pl. ed. 5: 315 (1754).
- Family: Polygalaceae
- Chromosome number: x= 14, 17; P. chinensis: 2n= 28; P. paniculata: 2n= 52-56; P. sibirica: 2n= (30, 32), 34, (68)
Major species
- Polygala polifolia Presl.,
- P. sibirica L.
Vernacular names
- Milkwort (En).
Origin and geographic distribution
Polygala comprises about 500 species and occurs in tropical, subtropical, temperate and montane regions throughout the world, except New Zealand. The majority of the species grow in tropical Central and South America, and secondary centres of diversity are found in North America and South Africa.
Uses
Polygala roots are pungent, sweet, warming and tranquillizing. Several Polygala species, such as P. sibirica in China, P. crotalarioides Buch.-Ham. ex DC. in the Himalayas, P. polifolia in southern India and Java, and P. senega L. (snake root) from northern America are known for the expectorant action of the roots, which are used for coughs, asthma, pulmonary catarrh and bronchitis. The roots of P. glaucoides L., occurring from Sri Lanka to South-East Asia, and P. senega, are also known to be active against snake bites. The roots of P. sibirica are a constituent of traditional Chinese and Japanese medicine mixtures for treating mental and neurological disorders. In Peninsular Malaysia, they are imported for use as a tonic. The leaves and roots of locally occurring P. polifolia and P. paniculata L. are used in the same way. In China, the roots of P. sibirica are applied to furuncles and painful swellings in the breast. They are also used to promote a clear mind, to dispel phlegm, as a remedy for heart trouble, head and chest pains, for reddish urine, jaundice, hysteria, and infantile convulsions. In Vietnam, a decoction of the roots is also employed for impaired memory and sexual impotency. In India, the roots of P. polifolia and P. chinensis are used for fever, dizziness and as an antiseptic. A sweetened infusion of P. paniculata is a remedy for gonorrhoea and lumbago. The pulverized leaves may be applied to wounds, but should be handled carefully since the sap causes inflammation if it gets in the eyes. In New Guinea, the women eat the flowers against infertility. In Indo-China, the leaves and stem of P. chinensis are used to treat congestion, the pith of the roots is prescribed to treat fever, inflammations of the throat, spermatorrhoea, and haematuria. In Java, an infusion of the leaves is taken for cough and asthma, and is a constituent in a remedy for diarrhoea. An infusion of the whole herb is recommended for chronic bronchitis.
In India, the tender leaves of P. polifolia are used as a vegetable in times of scarcity. They are said to have a pleasant flavour. In Java, the roots of P. paniculata are kept between clothes, because of their fragrance. P. butyracea Heck. is cultivated in West Africa for its fibre and as an oil-seed crop. It has been tried as an oil-seed crop in Peninsular Malaysia and Java, but the seeds ripened too unevenly to be useful.
Production and international trade
Polygala is only traded on a local scale in South-East Asia. The roots of P. sibirica are imported by the Chinese into Peninsular Malaysia and Vietnam. P. sibirica is cultivated for the roots in China and Japan, as is P. senega in Europe, but no information on production is available.
Properties
Many Polygala species contain saponins in their roots, but only limited tests have been performed to investigate the biological activity of these purified compounds.
The roots of P. senega ("Senegae Radix") contain 6-12% triterpenoid saponins: senegin II, III and IV. These are based on the aglycone presenegin to which 2 separate sugar groups are attached. Various other saponins, mainly artefacts depending on the conditions of hydrolysis, have been identified, together with several oligosaccharide multi-esters (10%). Besides saponins, the samples also contain a volatile oil with small amounts of methyl salicylate.
Isolated senegin II showed a hypoglycaemic effect in normal and streptozotocin-induced diabetic mice. Also, a syrup made from the roots is a well known and established expectorant, perhaps via a reflex mechanism in which irritation of the gastric mucosa by the saponins leads to expectoration. The roots of P. sibirica contain triterpenoidal saponins which are referred to as onji-saponins (A-G); they have a very similar composition as those from P. senega, based on the aglycone presenegin. The plant also contains xanthones (e.g. polygalaxanthone III), acylated sugars (tenuifolisides A-P) and a tenuifolic saponin.
Onji-saponin F has sedative properties. The effect of tenuifolic saponin on arterial pressure was investigated in rats. Systolic blood pressure of conscious and renovascular active hypertensive rats was measured by the tail cuff method, and treatment reduced the main arterial pressure by 21-50%, depending on the dose. However, it had no effect on carotid-occlusion-induced or ephedrine-induced hypertensive responses.
The compound 3,5-dimethoxy-4-hydroxycinnamic acid (= sinapinic acid) from the roots induced choline acetyltransferase activity in the cerebral cortex of basal forebrain-lesioned rats, and also induced nerve growing factor secretion in astroglial cells.
An aqueous extract of the roots of P. sibirica was investigated for its inhibitory effects on secretion of tumour necrosis factor-α (TNF-α) by primary cultures of mouse astrocytes. The extract inhibited interleukin-1 secretion, which elevates TNF-αsecretion, and also had an anti-inflammatory effect on the central nervous system. Other pharmacological effects of whole extracts include a reduction of catecholamine contents and tyrosine hydroxylase activity of PC12 cells (derived from rat adrenal pheochromocytoma, and demonstrating many properties of adrenal medullary chromaffin cells) by the butanol fraction of the methanol extract of the dried roots, and significant anthelmintic properties against Clonorchis sinensis by the aqueous extract of the aerial parts.
The roots of P. chinensis (synonym P. glomerata) contain polygala-saponins, and oligosaccharide polyesters: glomeratoses A-G. The roots also contain several flavonoids e.g. rutin, afzein.
The leaves and bracts of P. paniculata contain the anthocyanidins delphinin-3-bioside and cyanidin-3,5-dimonoside. An extract of the plant contains the coumarins aurapten, phebalosin, murrangatin, 7-methoxy-8-(1,4-dihydroxy-3-methyl-2-butenyl)coumarin and the diester 3'-acetyl-4'-benzoylkhellactone. Of the latter compounds, phebalosin has molluscicidal and fungistatic activity.
Description
- Annual or perennial herbs, shrubs or small trees, sometimes spiny.
- Leaves in general spirally arranged, entire.
- Inflorescence a terminal, axillary or supra-axillary raceme, subtended by a small, caducous or persistent bract, bracteoles 2, caducous or persistent.
- Flowers bisexual, zygomorphic; sepals 5, normally free, caducous or persistent, unequal, 2 inner ones largest, often petaloid (wings); petals 3, 2 upper ones basally adnate to the staminal tube, lower one boat-shaped (keel), clawed, entire or with a dorsal crest, crest consisting of 2 lobes, the latter entire or divided into a various number of appendages; stamens 8, monadelphous, anthers sessile or on a free filamentous stalk, basally attached, opening with only 1 terminal pore common to both cells; disk annular, or consisting of 1-2 short appendages, often persistent in fruit; ovary laterally compressed, 2-celled, each locule with 1 subapical ovule; style variable.
- Fruit a capsule, compressed contrary to the sept, mostly margined, sometimes winged, dehiscing by a marginal split, reniform to oblanceolate.
- Seed in Malesia usually dark and hairy, at micropilar side with a lobed or unlobed aril, at the opposite side usually with an elongate, black, glossy appendage (strophiolus).
- Seedling with epigeal germination; cotyledons ovate, rounded; first pair of leaves ovate to elliptical, reddish green.
Growth and development
Polygala species can be found flowering throughout the year in everwet climates. In seasonal climates they flower early in the summer season, and complete their life cycle in 4-5 months. Self-pollination probably occurs in all species, although the flowers of the majority are attractive to insects, and adaptations to pollinating insects occur.
Other botanical information
In Malesia, Polygala is divided into 4 little-related sections, of which the largest one is section Polygala, probably an artificial assemblage. Considerable taxonomic confusion exists in some Polygala species. Following the latest revision, the name P. chinensis has been misapplied in nearly all cases for P. polifolia, but also for the closely resembling P. triflora L. and P. glaucoides. P. glomerata Lour. has become a synonym of P. chinensis, because the first name was illegally introduced to prevent the confusion in P. chinensis. In several Polygala species monstrous flowers sometimes occur, with supernumerary flower parts especially in the calyx; these flowers are normally sterile. The name milkwort was given to Polygala because it was previously thought that the plants increased the yield of cow milk.
Ecology
The herbaceous Polygala species are sun-loving, and grow in open woodland, often grasslands in areas with a seasonal climate, in contrast to the shrubby species, which are restricted to the undergrowth of the rain forest.
Propagation and planting
The seeds of P. chinensis show dormancy. When the seed coat is removed or deeply scarified, germination reaches 100% or 70% respectively, suggesting the presence of a germination inhibitor in the seedcoat. Washing the seeds in running water for 10 days results in 60% germination. Maximum germination occurs between 25-28 °C. Diffuse daylight gives better results than either continuous light or dark periods, and red light stimulates germination of scarified seeds more than other wavelengths. The optimum pH for germination was 6.5, and gibberellic acid is effective in breaking the dormancy of both scarified and untreated seeds, at rates of 100% and 70% respectively.
Diseases and pests
In Indonesia P. paniculata is infested by the cinchona mite (Tetranychus cinnabarinus) and the orange mite (Brevipalpus obovatus).
Harvesting
Polygala plants are dug up completely in order to obtain the roots. When only the aerial parts are needed, plants are cut off above-ground.
Handling after harvest
The roots and aerial parts of Polygala are used fresh or dried for storage.
Genetic resources and breeding
The Polygala species described here are widespread in anthropogenic habitats and are not at risk of genetic erosion. Neither germplasm collections nor breeding programmes are known to exist.
Prospects
Saponins from Polygala are well-known expectorants, with a reasonably well-established history of use. A local source of these species might therefore be of interest for rural communities. For instance, P. sibirica is not cultivated at present in South-East Asia, but due to its medicinal prospects, cultivation could be possible in mountainous areas.
Literature
- Adema, F., 1966. A review of the herbaceous species of Polygala in Malesia (Polygalaceae). Blumea 14(2): 253-356.
- Kim, H.M., Lee, E.H., Na, H.J., Lee, S.B., Shin, T.Y., Lyu, Y.S., Kim, N.S. & Nomura, S., 1998. Effect of Polygala tenuifolia root extract on the tumor necrosis factor alpha secretion from mouse astrocytes. Journal of Ethnopharmacology 61(3): 201-208.
- Lee, M.K. & Kim, H.S., 1996. Effects of the root of Polygala tenuifolia on catecholamine biosynthesis in PC12 cells. Archives of Pharmacological Research 9(1): 74-76.
- Teresa, M.V.M. & Avita, S., 1989. Dormancy and germination behaviour of Polygala chinensis L., a medicinal plant. Feddes Repertorium 100(7-8): 357-362.
- van der Meijden, R., 1989. Polygala. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Series 1, Vol. 10. Kluwers Academic Publishers, Dordrecht, the Netherlands. pp. 459-482.
- Yabe, T., Iizuka, S., Komatsu, Y. & Yamada, H., 1997. Enhancements of choline acetyltransferase activity and nerve growth factor secretion by Polygalae radix-extract containing active ingredients in Kami-untan-to. Phytomedicine 4(3): 199-205.
Selection of species
Authors
- Rina R.P. Irwanto
