Plantago (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Plantago L.

Protologue: Sp. pl. 1: 112 (1753); Gen. pl. ed. 5: 52 (1754).

Family: Plantaginaceae

Chromosome number: x= 4, 5; P. afra: 2n= 12, P. asiatica: 2n= 12, 24, 36, P. lanceolata: 2n= 12 + 0-1B, 24, P. major: 2n= 12, 24, P. ovata: 2n= 8, 16

• Plantago major L.

• Plantain (En; a confusing name as in the tropics it is mainly used for the cooking banana).

Plantago consists of approximately 250 species and is cosmopolitan except the polar regions. It is essentially temperate in its natural distribution. Some species, particularly P. major and P. lanceolata, are extremely widespread, throughout temperate regions and also penetrating into tropical highland regions. P. major is the most widespread species in South-East Asia, and P. lanceolata is only very locally naturalized.

The seed or seed coat of e.g. P. afra and P. ovata are widely used as laxative, but also to treat dysentery of amoebic and bacillary origin and diarrhoea. Products containing seed preparations are taken by many people worldwide to control bowel function: to treat habitual constipation, as supportive therapy in diarrhoea and with irritable bowel syndrome. Seed husks ("Psyllium husk") have become very popular in breakfast foods in the United States. They may also be a useful supplement in weight control diets by affecting fat intake and effecting a subjective feeling of fullness.

The seeds of P. asiatica and P. major are considered as expectorant, diuretic and antimicrobial in Chinese and Vietnamese medicine.

In China and Japan, the aerial parts of these plants (known as "Plantago herba") are commonly used to treat coughs, bronchitis and asthma. Plantago leaves are used traditionally topically as an emollient and itch-relieving treatment against dermatological complaints and eye irritation. A poultice of 10% of dried and pulverized leaves of P. major is used to treat eczema, but juice from pressed fresh leaves, extracts in 96% alcohol and maceration products are also used. In modern phytotherapy aerial parts or leaves of P. major ("Plantago major herba") and P. lanceolata ("Plantago lanceolatae herba/folium") are used to alleviate irritation in catarrh of the upper respiratory tract. Macerates, fluid extracts, syrups and expressed juice from the fresh plant are all used for treating inflammation of the mouth and throat, and externally for inflamed skin.

The seed mucilage is also used in cosmetics (e.g. in lotions and hair wave sets) and as a basic stabilizer in the ice-cream industry. It is also used in the preparation of chocolate; it is an excellent thickener. The seeds can be used as a source of a low-cost gelling agent for tissue culture. The quality is reasonably comparable with that of agar, and the costs are only about 10% of those for agar.

Leaves are edible and sometimes eaten as vegetable. In some areas, P. lanceolata is considered a good fodder; it is reported to be a good source of calcium, potassium, sodium, cobalt, phosphorus and chlorine.

India is an important exporter of seed husks (mainly of P. ovata and to a lesser extent of P. afra), especially to the United States, where annual imports were worth about US$ 3.5 million in the late 1980s. It has been estimated laxatives containing Plantago are daily used by about 4 million Americans.

The amount of mucilage in the seeds can be substantial (up to 30% in P. ovata). Being located only in the epidermis of the testa, it mainly consists (up to 85%) of a water-soluble polysaccharide fraction (arabinoxylan) in which D-xylose is the main constituent. The backbone is a xylan polymer with 1-3 and 1-4 linkages and no apparent regularity in their distribution, with the xylose monomers substituted on C-2 or C-3 by L-arabinose, D-xylose and α-D-galacturonyl-L-rhamnose. The quality of the mucilage is evaluated by measuring its swelling index, which should exceed 9. P. lanceolata and P. major provide a similar mucilage which is rich in D-galactose and L-arabinose and contains nearly 40% uronic acids. On hydrolysis the mucilage of P. afra yields D-xylose (about 70%), L-arabinose (about 10%), α-D-galacturonyl-(1-4)-L-xylose and D-galactose; the swelling index must be at least 10. The seeds also contain 5-10% lipids with unsaturated fatty acids, sterols, 15-18% proteins, traces of cyclopentanopyridine-type alkaloids and the iridoid aucubin. An isomer of ricinoleic acid, β-hydroxyolefinic acid 9-hydroxy-cis-11-octadecenoic acid, has been found as a minor constituent (1.5%) of the seed oil of P. major.

The seeds owe their laxative properties to the very hydrophilic polysaccharides. The action is purely mechanical and linked to the mucilage taken together with abundant fluid; the polysaccharide macromolecules absorb much water and form a gel that increases stool bulk, stimulates peristalsis and facilitates bowel movements. The effect has been confirmed by several clinical studies. In double-blind, placebo-controlled studies with patients suffering from chronic constipation, administration of Plantago seeds (or preparations containing seed testa) showed good results, increasing the frequency and decreasing the consistency of stools. No adverse effects were observed and, notably, no flatulence occurred, as often seen in patients taking bran. On the other hand, the mucilage can also be used as supportive therapy in diarrhoea: by absorbing water, the transit period of the bowel contents is extended. The mucilage has also frequently been reported to lower blood sugar and cholesterol, similar to the activity following the administration of galactomannans or pectins, although in general these effects are only very slight and often not demonstrated in clinical studies. In some tests, however, it was demonstrated that P. afra mucilage is useful as an adjunct to dietary therapy in patients with type II diabetes. A test in which patients were treated with a commercially available preparation of P. ovata showed positive effects on internal bleeding haemorrhoids. P. ovata seeds might be as effective as mesalamine to maintain remission in ulcerative colitis.

P. major seeds, administered orally, showed a significant haemostatic activity in the treatment of menorrhagia in a preliminary clinical study in India. When tested under standardized conditions in a placebo-controlled double-blind crossover model in Vietnam, no influence of the drug was recorded on the urine output and sodium excretion.

The reticulo-endothelial system-potentiating and alkaline phosphatase-inducing activities of the mucilage from P. asiatica have been found to be markedly enhanced when the mucilage was de-O-acetylated. The deacetylated product showed considerable anti-complementary activity as well as considerable hypoglycaemic activity on administration to mice.

Administration of the seeds has no serious side-effects; only a few exceptional cases of allergic reactions have been documented. However, the husks are known to elicit respiratory allergic reactions after inhalation or ingestion by sensitized individuals. Immunological, biochemical and microscopic findings suggest that other contaminating seed components are primarily responsible for the allergenicity of commercial-grade Plantago husk powder rather than the husk itself. The preparations are contra-indicated if there is pyloric stenosis and abnormal narrowing of the gastro-intestinal tract, and must be used with care, to avoid product stagnation in the oesophagus in the case of bedridden patients with megacolon by alteration of colon motility, and in patients with diabetes that is difficult to control.

Leaves of P. major contain iridoids and phenols: flavonoids, phenolic acids and phenylpropanoic esters of glycosides (verbascoside, plantamajoside). The iridoid glucoside majoroside has also been isolated from P. major, along with aucubin and catalpol. P. lanceolata leaves also contain iridoids (1.9-2.4%) such as aucubin, catalpol and asperuloside, flavonoids and phenolic acids. Aucubin glycoside can be detected by thin-layer chromatography of a methanol extract. It can also be quantified by high pressure liquid chromatography. The proposed levels for the French pharmacopoeia are 0.5% for P. major and 1.0% for P. lanceolata. The content of aucubin in P. asiatica is reported in Vietnam to decrease gradually from the roots to the flowers and leaves. The drying temperature affects the content of aucubin; plant material dried at 80°C is reported to contain higher concentrations of aucubin than plant material dried at 40°C. Analysis of dried samples sold on markets in Vietnam showed that aucubin was absent, but that the allantoin content was often high (up to 80%) which makes the drug effective for the treatment of burns and stomach ulcers. The iridoids have a potential role in anti-inflammatory activity. Aucubigenin liberated from aucubin by glycosidases present possesses antibacterial activity. 3,4-Dihydroxyphenethyl alcohol-6-O-caffeoyl-β-D-glucoside, the phenylethanoid glycoside plantasioside, acteoside (verbascoside), plantaginin, plantamajoside and the phenylpropanoid glycoside hellicoside have been isolated from aerial parts of P. asiatica. Acteoside showed high inhibition of lens aldose reductase. Plantamajoside and hellicoside showed high inhibition of cyclic AMP phosphodiesterase and 5-lipoxygenase, which might have some correlation with the therapeutic effect of the herb as anti-inflammatory and anti-asthmatic. Acteoside and plantamajoside, which have also been found in P. lanceolata, showed inhibitory effects on arachidonic acid-induced ear oedema in mice. A hot-water extract of the whole plant of P. major exhibits diuretic activity and dissolves kidney stones. A chromatographic fraction of dried leaves was found to promote wound healing. Aqueous extracts of P. lanceolata showed immunomodulatory effects; in tests they stimulated the production of anti-SRBC (IgG) antibodies in mice and stimulated the release of angiogenic factors by mouse spleen cells and human mononuclear blood cells, and in vitro a P. lanceolata polysaccharide fraction showed an increase in phagocytosis of granulocytes. Liquid P. lanceolata preparations are said to have hepatoprotective (chloroform, α-amanitin) activity, and might also offer protection against adverse effects of cytostatic agents (e.g. 5-fluorouracil). In vitro experiments showed a mortality of 76% of the zooflagellate Giardia duodenalis when treated with a P. major extract.

In the United States, interplanting peach trees with P. lanceolata reduced nematode numbers (Criconemella xenoplax), but not to acceptable levels to justify commercial control. In tests with germinating lettuce seeds, aqueous extracts of P. lanceolata and P. major showed allelopathic activity.

Pollen, particularly that of P. lanceolata, may cause allergic reactions in sensitive persons.

The seed of flax (Linum usitatissimum L.) also contains mucilage which can be used as "bulk laxative" just like that of Plantago seeds. All parts of some Malvaceae such as the European Althaea officinalis L. and Malva sylvestris L. contain mucilage which is used orally in the adjunctive therapy of the painful component of spasmodic colitis and for symptomatic treatment of cough, and topically as emollient and to treat itch. In India, Plantago seeds are frequently mixed with those of Salvia aegyptiaca L., which also yield copious mucilage.

Iridoid glycosides are fairly common in dicotyledonous Angiosperms. They are, for instance, present in Scrophulariaceae such as Verbascum species, which are used in phytotherapy for similar purposes as Plantago. Aucubin is also present in the genera Aucuba (Cornaceae) and Garrya (Garryaceae).

• Annual or perennial herbs up to 50(-80) cm tall, stemless or with branched stem.
• Leaves in basal rosettes or opposite, with distinct, parallel veins, usually distinctly petiolate when in rosettes and without distinct petiole when inserted on stems; stipules absent.
• Inflorescence a pedunculate, bracteate spike.
• Flowers actinomorphic, usually bisexual, 4-merous; sepals connate at base or free, equal or nearly so, imbricate, scarious, persistent; corolla gamopetalous, usually with patent or deflexed imbricate lobes, scarious, persistent; stamens inserted on corolla tube, alternating with corolla lobes, exserted, anthers conspicuous; ovary superior, 2-4-locular, style 1 with a stout pilose stigma, protruding.
• Fruit a circumscissile capsule, few- to many-seeded.
• Seeds with endosperm and straight embryo; testa thin, often mucilaginous when wet.
• Seedling with epigeal germination; cotyledon sessile or shortly petiolate, sheathed at base; hypocotyl elongate, epicotyl absent; first leaves alternate or opposite (in species developing stems).

In tropical climates Plantago may flower all year round, and a life cycle may be accomplished in 6 weeks. The flowers remain functionally female much longer than functionally male. The stigma is already protruding and receptive when other flower parts are still in bud, whereas it can still be functional after the stamens have withered. P. lanceolata is gynodioecious: specimens can be found with either bisexual flowers or only female ones. In P. lanceolata cross-pollination is the rule, whereas in P. major self-pollination is common. The flowers are wind-pollinated.

The seeds are already ripe 2-3 weeks after fertilization. Seeds readily adhere to animals or people thus facilitating their dispersal. They can also be transported by water. Perennial Plantago species may live for up to 15 years; in cultivation in Turkmenistan they may last up to 8 years.

P. major and P. asiatica are probably often confused as they are difficult to distinguish. However, they are reported to be clearly distinguishable in Japan by anatomical characters of seeds and leaves. Some authors consider both species to be conspecific.

P. afra is closely related to P. arenaria Waldst. & Kit. (synonym: P. indica L.), which in southern Europe is a source of mucilage with medicinal value too. Some cultivars of P. afra and P. ovata were developed in India in the late 1980s.

P. ovata and P. afra seem to be occasionally confused in the literature on cultivated Plantago in India, although they can easily be distinguished by leaves in rosettes (P. ovata) or on distinct, much-branched stems (P. afra).

P. lanceolata and P. major occur in areas disturbed by man. Because of their morphology they are well adapted to withstand the trampling of livestock and humans. Once established in fields, they can become a noxious weed in e.g. coffee, onions, cotton and, in particular, in cereals like rice.

In general, cool and dry weather is favourable to crops of P. afra and P. ovata; they require dry weather from flowering until seed maturity (about 2.5 weeks). P. major is more tolerant of compacted soils than P. lanceolata, so the former appears frequently in almost pure stands on the edges of paths, whereas the latter often occurs in grasslands. P. major is more tolerant of waterlogging, whereas P. lanceolata is more drought tolerant. P. afra and P. ovata tolerate dry, sandy soils extremely well. They are grown in India on medium to poor sandy soils; however, they grow best on rich, well-drained loamy soils.

P. major reproduces mainly by seed. A seed production of up to 14 000 seeds per plant has been reported for this species. Plantago may be multiplied by seed or vegetative means. For large-scale seed production of P. ovata, propagation is by seed. The seed is broadcast or drilled in rows 30 cm apart, so 6-13 kg/ha of seed is needed. P. lanceolata may also be propagated by new buds arising on the thick underground stem. The 1000-seed weight of P. afra is 1.1-1.2 g. Plant spacing in experimental plantings of P. afra in Thailand was 25 cm × 10-30 cm. Interplanting of P. ovata with poplar (Populus spp.) has shown good results in India. Seeds may exhibit dormancy, which can be broken by several months of dry storage at room temperature or by a few weeks at 5°C. Seed 1-5 years old shows better germination rates than fresh seed. Seed has remained viable in the soil for over 60 years.

In India, P. ovata as a crop is irrigated. Weeding is carried out when the crop is about 6 weeks old.

P. lanceolata may serve as a host for Pseudomonas viridiflava and P. syrinage which can cause a serious bacterial disease in tomato. In India, P. major has been reported a host for Meloidogyne hapla which causes root galls in Irish potato. Meloidogyne species have also been identified from P. lanceolata. Larvae of the fruit weevil Naupactus xanthographus, a pest of several fruit trees, have been observed on P. major. P. ovata has been reported to be a host of the coriander aphid (Hyadaphis coriandri) which can be a pest of coriander, fennel, dill and celery in India.

In Thailand, harvesting P. afra seeds 17 days after the first inflorescence was mature gave the highest seed yield. This means that the crop can already be harvested about 10 weeks after sowing. In western India, P. ovata is harvested after 3-4 months. Plants are cut about 15 cm above the ground early in the morning to prevent seed shedding.

Care should be taken when collecting P. major from the wild for medicinal purposes, since plants may contain high concentrations of heavy metals like lead and cadmium as they often grow along the roads.

The seed yield of P. afra in experimental plantings in Thailand was estimated at about 1150 kg/ha. The seed yield of P. ovata in India is 500-1100 kg/ha. The yield of husks is approximately 25% of the seed weight.

Plants harvested for seed are threshed, winnowed and sieved until the seed is clean. The husk is removed by mechanical milling and subsequent winnowing and sieving.

The Plantago species treated here are common in anthropogenic habitats, and there is no reason to consider them as liable to genetic erosion. Except for P. major and P. lanceolata, the Plantago species highlighted here are not yet found in Malesia. This implies that the genetic variability of Plantago is limited in the region.

The uses of Plantago orally to treat digestive and bronchial disorders and topically to treat skin disorders are very widespread. Modern research seems to confirm the activity of the drug, although information is far from complete. This, plus the ease of cultivation, seems to justify advocating planting Plantago for medicinal purposes. However, more research is needed to achieve a proper standardization of the drug, and to establish the potential in the Malesian region of Plantago species that are currently cultivated in neighbouring countries like Thailand. Leaves of P. asiatica and P. lanceolata have been recorded as a promising vegetable in regions with malnutrition.

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• Ravn, H., Nishibe, S., Sasahara, M. & Xuebo, L., 1990. Phenolic compounds from Plantago asiatica. Phytochemistry 29(11): 3627-3631.
• Sas, A.C., 1984. Plants and health. Eastern Publishing Association, Manila, the Philippines. p. 181.
• Tomoda, M., Takada, K., Shimizu, N., Gonda, R. & Ohara, N., 1991. Reticuloendothelial system-potentiating and alkaline phosphatase-inducing activities of Plantago-mucilage A, the main mucilage from the seed of Plantago asiatica, and its five modification products. Chemical and Pharmaceutical Bulletin 39(8): 2068-2071.

• Plantago afra
• Plantago asiatica
• Plantago lanceolata
• Plantago major
• Plantago ovata

• Lilis Pangemanan