PLANTAGINACEAE

The Plantaginaceae or plantain family consists of three genera of widely distributed herbs and sub-shrubs of the temperate region.

There are many native and naturalised species of plantain. Three species of Plantago, P. lanceolata, P. major, and P. psyllium are commonly used in traditional western medicine as well as the less well-known P. indica and in India P. ovata.

Plantago lanceolata

Ribwort, narrow-leaved plantain

Description

A perennial herb with a persistent taproot. Leaves all radical, rosulate, hairy with a 1–7 cm long petiole, channelled, and with a silky white tuft of hairs and often purplish at the base. Lamina 2–20 × 0.5–4.8 cm, linear lanceolate to elliptic-lanceolate, 3–7 veined, glabrate or hairy especially on the veins beneath, entire or slightly toothed. Scape (flower stalk), 12–70 cm long, sparsely or densely hairy, strongly ribbed. Flower spike very congested, more or less oblong and about 6 cm long. Bracts 3–6 mm long, acuminate with a green keel and the upper part of the bract otherwise brown. Sepals 4, 2.7–3.5 mm long, unequal with the anterior pair fused, midrib green otherwise brown. Corolla tube equal to calyx with lobes about 2 mm long, ovate. Stamens glabrous, exserted, with either white or yellow anthers. Styles exserted up to 15 mm long, densely hairy. Capsule usually 2.5–3.5 mm long, ellipsoid and two-seeded. Seeds 2–3 mm long, ellipsoid, medium to dark brown. Flowers present except in winter. In warmer regions of many countries it flowers more or less all year round.

Taste—mucilaginous and somewhat salty and bitter.

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Family Plantaginaceae

Habitat and cultivation

Native to Europe and naturalised elsewhere in open areas, river beds and coastal areas. Grown from seed or transplanted from the wild when small into any garden soil. Frost and drought resistant.

Parts used

The leaves harvested just prior to, or at the start of, flowering.

Active constituents

1) Iridoids (max 9%) including mainly aucubin and its metabolite catalpol1 as well as asperuloside and verbenalin.2 These vary with genetic profile and growth conditions.3,4 Also damage to the plant induces increased levels of iridoid glycosides.5 Aucubin levels are highest in mid-autumn.6

2) Phenylethanoids including acteoside (verbascoside) and plantamajoside7,8

3) Flavonoids including luteolin and its derivatives9

4) Mucilage (2–6.5%) composed of polysaccharides10

5) Tannins (6.5%)

Also contains phenolic and silicic acids. Enzymes occur in the fresh juice and in water extracts.11

Nutritional constituents

Minerals: Silicon, zinc and high levels of potassium

Actions

1) Diuretic

2) Anti-inflammatory

3) Antihaemorrhagic

Scientific information

Both P. lanceolata and P. major are valued as medicinal herbs with some practitioners favouring one over the other. P. lanceolata has been especially associated with treatment of the respiratory tract whereas P. major is more favoured for treatment of urinary problems. However, they are probably very similar in their pharmacological actions and are considered identical as far as German Commission E monographs are concerned.

Both species have a long history of medicinal use throughout the world having been used to treat a multitude of health problems. There has been very little modern scientific validation of these uses. German Commission E has approved the internal use of P. major/P. lanceolata for catarrh of the respiratory tract and inflammation of oro-pharyngeal mucosa, and external use to treat skin inflammation.

Interest has been shown in the use of P. lanceolata as a pasture feed for animals as it has proved beneficial to their health and may reduce the need for antibiotic growth promoters.12

In vitro—The polysaccharides have good antioxidant activity,13 in the whole extract this activity has been somewhat variable.12,14 The herb also inhibits COX-2 activity15 and this together with any anti-oxidant capacity could help explain its historical use as an anti-inflammatory.

The Plantago spp. have been used traditionally for treating cancer and both P. lanceolata and P. major have activity against cancer cells, an action also displayed by a major flavonoid constituent, luteolin-7-O-β-glucoside, present in both.16

Aucubin is known to have bactericidal, bacteriostatic, hepatoprotective, anti-inflammatory, antitumoral and collagen synthesis stimulating activities.17 Acteoside also has a range of physiological activities, it is anti-inflammatory,7 antioxidant,7 anticancer18 and cytoprotective.19

In vivo—The fresh juice of the herb has been used to treat parasitic worms but both water and ethanol extracts may also be effective based on animal studies.20

Medicinal uses

Respiratory tract

Gastro-intestinal tract

Urinary tract

The seed may be used in the treatment of cystitis too.

Externally

The leaf can be applied locally to:

Pharmacy

Three times daily

Infusion of dried herb –   2–4 g
Tincture 1:5 (45%) –   2–4 ml
Fluid Extract (25%) –   2–4 ml

Precautions and/or safety

In a standard test P. lanceolata was not genotoxic.21

Historical uses

Blisters, ulcers, stings, bites, conjunctival congestion, inflammation; anthelmintic.

Plantago major

Rat-tail plantain, broad-leaved plantain

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Family Plantaginaceae

Description

A short-lived perennial herb with a stout caudex and many large adventitious roots, or occasionally, with persistent, well-developed primary roots. Leaves all radical, rosulate with 1–20 cm long petioles, channelled at the base. Lamina 21 × 16 cm, ovate to sub-orbicular, generally puberulent, at least on the main 5–7 veins beneath, generally glabrous, entire or remotely dentate. Base truncate to cordate, apex rounded to obtuse. Scapes 5–80 cm long, not ribbed, and generally hairy especially near the base. Spikes dense 1.5–30 cm long, narrow-cylindric. Bracts ovate, larger than calyx. Sepals 1.5–2 mm long, broad ovate. Corolla tube about the same size as the calyx. Capsule usually 2.4–4 mm long, broad-ellipsoid, 6–16 seeded. Seeds 1–1.8 mm long, rugose; dark red, brown, dark brown or black. Flowers early spring to autumn.

Habitat and cultivation

Native to Eurasia and naturalised elsewhere in moist situations. Grows and seeds freely and may be transplanted into gardens. It is a very variable species in some countries.

Parts used

The leaves harvested just prior to, or at the start of, flowering.

Active constituents

1) Iridoids including aucubin22

2) Phenylethanoids including plantamajoside23

3) Flavonoids including apigenin, luteolin, baicalein and their derivatives24

Also contains tannins and organic acids including caffeic, ferulic and chlorogenic, the triterpenoids ursolic25 and oleanolic acids,24 an enzyme that has collagenase activity (named plantagolisin) in fresh juice26 and some fatty acids.27

Nutritional constituents

Vitamins: B-carotene and carotenoids, C and K24

Minerals: Calcium, potassium, sulphur and also a high content of trace minerals

Actions

1) Anti-inflammatory

2) Diuretic

3) Antihaemorrhagic

Scientific information

In vitro—Although the aqueous extract of the herb has weak antibacterial, antifungal and antiviral activity against some test organisms,28–30 a few of the individual constituents are strongly antimicrobial.30 The herb has antibacterial activity, including against Salmonella typhimurium, Staphylococcus aureus, Escherichia coli and Bacillus subtilis, the extracting medium may determine the level of this activity.31 It also has antiprotozoal activity against Giardia duodenalis, comparable to that of a pharmaceutical preparation.32

Water extracts inhibit cancer cell proliferation (a number of its constituents are also cytotoxic)33,34 and are immunomodulatory.28,33

A number of constituents are anti-inflammatory, through inhibition of COX activity, including ursolic and oleanolic25 and the fatty acids.27

In vivo—The herb was beneficial in the treatment of chronic bronchitis.35

Although there are no modern studies in vivo into the effects of P. major a review suggests it has antimicrobial (antiviral and antibacterial) action when used topically even though in vitro studies indicated low activity.24

Medicinal uses

Gastro-intestinal tract

Urinary tract

The seed may be used in the treatment of cystitis too.

Externally

The leaf can be applied locally to:

Pharmacy

Dosage three times daily

Infusion of dried herb –   2–4 g
Tincture 1:5 (45%) –   2–4 ml
Fluid Extract (25%) –   2–4 ml

Precautions and/or safety

Most standard tests show P. major is not genotoxic21,36 with the exception of one non-human based assay.37

Interactions

There has been a report of P. major elevating serum digoxin levels which has since been ascribed to contamination of a commercial preparation of the herb with Digitalis lanata.38 Measurements of levels of digoxin and 13 other drugs including tricyclic antidepressants, anti-epileptics, antibiotics and analgesics showed that P. major does not affect their therapeutic monitoring.39

Historical uses

P. major was used to stop bleeding from many areas—reproductive tract, lungs, urinary tract and digestive tract including from ulcers; as an antidote to the poison of snakes and mad dogs and the stings of insects and nettles; to cool hot conditions ranging from burns to gout to fevers; dislocated joints. Coughs due to heat; ague; to treat worms. The powdered seeds were given to treat “epilepsy, vomiting, lethargy, dropsy, jaundice, strangury and liver obstructions”. The juice of the herb was mixed with Rose oil for headaches and lunacy; eye and ear pain; to restore hearing; toothache. Externally also for scabs; itch; tetters; ringworm; shingles; malignant and leishmanial ulcers; oral thrush.

Plantago psyllium

Psyllium, flea seed†

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Family Plantaginaceae

Description

A branched annual 35–60 cm tall in flower. Leaves linear, entire, sticky-hairy, grey-green, to 7.5 cm long, opposite or in whorls of 3–6 leaves. Flowers small, numerous, white, in globose spikes to 1–1.5 cm long, on long peduncles. Flower bracts scarious-margined, rounded at apex. Seeds 2–3 mm long, flea-shaped and dark glossy brown.

Habitat and cultivation

Native to the Mediterranean it grows freely in North Africa, France and Spain, in poor, dry, sandy soils and full sun. May be grown elsewhere from seeds sown in spring in light soil and full sun. Selfsows freely.

Taste—bland and mucilaginous.

Parts used

The seeds (rubbed out of their coats when ripe) and the husks.

Active constituents

1) Mucilage (up to 30%) consisting predominantly of polysaccharides.40,41 The huskor outer seed coat contains around 85% mucilage42

2) Monoterpene alkaloids (seeds)

3) Triterpenes including stigmasterol and β-sitosterol (husks)43

4) Phenylethanoids including acteoside and isoacteoside (seeds)44

Also contains a small amount of acubin (seed), sugars and fixed oils rich in polyunsaturated fatty acids—linoleic, oleic and palmitic (husks).43

Actions

1) Bulk laxative

2) Demulcent

Scientific information

Seeds of the three species P. ovata, P. indica and P. psyllium have been official medicines.45 These plus P. ovata husks are approved by German Commission E for the treatment of chronic constipation, irritable bowel syndrome and diarrhoea.

These species of the western Plantago family have been best studied in recent times as they have become important medicines particularly with regard to bowel function. The husks are preferred because they contain more fibre, 67% of which is soluble. (The soluble fraction in the seeds is only 47%.) The mucilage in the husk is composed of 3 main fractions—one representing about 55% is a highly branched arabinoxylan polysaccharide, believed to be a key factor to the herb's activity as a laxative and in helping with lipid reduction. The second of about 15% is viscous in nature and the rest is composed of insoluble fibre.41

Many studies have been conducted into the medicinal benefits of psyllium, some of them driven by commercial interests so that the dosage form used can be variable and may account for some of the discrepancies found.

Gastro-intestinal function

The seeds of all the medical Plantago species may be used to help bowel function, however it is usually P. psyllium, P. indica and P. ovata seeds or husks that are used for this purpose. The husks of the first two species are known as psyllium whilst the latter is referred to as ispaghula. In practice this distinction is not necessarily made and the species are often used interchangeably.

The particular structure of the branched arabinoxylan confers activity on the herb as it is resistant to human enzyme digestion and fermentation by gut flora.41,46 This part of the mucilage, which is capable of holding a good proportion of water, reaches the colon intact where it bulks up the stools and makes their passage easier47 as well as encouraging better peristalsis and bowel motility.48–51 Stools become more hydrated, more frequent, have increased weight48 and are more viscous,51 providing a lubricant effect so that the consequent laxative action of the husks is both gentle and non-irritating.

The viscous fraction of the mucilage does not alter moisture content of stools or affect lipid metabolism but is fermentable by flora, as is a small proportion of the arabinoxylan and insoluble fractions. This process results in the production of short chain fatty acids as well as gas.52 Psyllium is considered a prebiotic as it favours the growth of beneficial intestinal flora.53

One of its main uses has been to treat constipation. It does not seem to alter gastro-intestinal transit time in healthy individuals54 but increases it in those with constipation55 and decreases it in those with diarrhoea.56,57

Chronic constipation has been defined as difficulty in passing motions, infrequent motions or both, persisting for a minimum of 3 months in the preceding 12 months.58 Studies have shown that psyllium fibre gives good improvement in this condition.59–61 It was more effective than many other laxatives resulting in better formed motions62 with less side-effects.63 It can be safely used to treat constipation in elderly people (where it has often been combined with senna)64,65 and promoted more frequent bowel function in patients with Parkinson's disease.66

The mucilage can also improve loose motions in diarrhoea by binding the fluid contents of the colon and psyllium has been successfully used in clinical trials to treat diarrhoea whether chronic (better effect than loperamide),67 in children,68 due to radiation therapy or drugs such as anti-obesity lipase inhibitors or70 protease inhibitors.71 It has also been effective in reducing faecal incontinence.72

It has been used with benefit in the treatment of:-

Endocrine

Sufficient dietary fibre eaten several hours before or as a part of a meal can reduce postprandial blood glucose and insulin levels.84,85 The process may in part be due to an increased transit time through the small intestine which reduces carbohydrate digestion and the opportunity for glucose absorption86 or perhaps by reducing enzyme contact with carbohydrates thereby slowing glucose uptake (see Avena). In addition a “second meal” effect has been described where eating a second meal after the initial ingestion of the fibre can still reduce plasma glucose levels from this later meal87,88 (not corroborated in another study94). Furthermore a high soluble fibre diet also seems to improve peripheral insulin sensitivity in normal people.88

These actions would be expected to have particular benefits for treating diabetes and a large number of studies have established that using the herb produces a dose-dependent improvement in glucose control. When used in conjunction with standard pharmaceuticals and/or diet psyllium improved blood glucose and associated factors like serum lipid levels and glycated haemoglobin in type 2 diabetics.89–94 Bowel function in those diabetics with hepatic encephalopathy95 was improved and uric acid levels also decreased.91 An additional advantage for type 2 diabetics may be weight loss96 as it appears to reduce feelings of hunger and give a subjective feeling of fullness97,98 without slowing gastric emptying.99

Psyllium also improved blood glucose (and serum) lipid levels in obese young people.100

Serum lipid levels

Dietary fibre has been shown to benefit serum lipid levels although the extent of this is controversial. The mechanism by which serum cholesterol is lowered is not fully understood but seems to be due to the fibre binding bile acids in the intestinal lumen which both prevents their re-absorption and increases their consequent excretion.101 The loss of bile acids increases their synthesis from cholesterol, effectively reducing serum levels. Increased excretion of bile acids has also been somewhat controversial, some researchers finding no evidence of it, and this proposed mechanism may therefore be too simplistic.103 However there are other ways by which psyllium may affect lipid levels. It increases the excretion of fatty acids and decreases fat absorption when the two are eaten in the same meal;102 the short chain fatty acids produced as byproducts of mucilage fermentation may further reduce serum cholesterol by inhibiting its dietary absorption.103

Psyllium has been considered one of the more effective fibres for lipid reduction in people with normal or raised cholesterol.104,105 There are many trials showing lowered levels of total cholesterol and LDL cholesterol in patients with hyperlipidaemia and hypercholesterolaemia106–112 (not corroborated113,128). Reviews of available data suggest psyllium can alter LDL cholesterol but the range varies between –24% to +3%.88,114 In children with hypercholesterolaemia it reduced LDL-cholesterol by between 7–22.8%.100,115 Some trials found cholesterol reduction by psyllium was as good as that achieved through lowering dietary fat intake,116,117 and may be as effective as statins in reducing LDL cholesterol.118 It has been suggested that used in conjunction with lipid lowering drugs psyllium may enable the effective drug levels to be reduced119 also helping to reduce their drug-induced gastro-intestinal side-effects.120 Whilst a meta-analysis concluded that soluble fibre, including psyllium, does reduce cholesterol levels the large discrepancy across trials was put down to variables like dosage and study design.104 It has been reported for example that psyllium may be more effective when consumed as part of the meal,121 that the effects differ by gender and hormonal status—being more beneficial to men122–124—and age too may be a factor, being less beneficial in older people (over 60).125

There are also conflicting reports of the benefits of husks compared to the seeds in cholesterol reduction. Some research has shown husks improved the lipid profile in patients with cardiovascular disease more effectively than the seeds126,127 whilst another reported that only the seeds were effective.128

Psyllium may help reduce the risk of gallstone formation in people on a low calorie, weight loss diet129 and may be beneficial when used in conjunction with pharmaceuticals in the treatment of chronic cholestatic liver disease.130

Colon cancer

High fibre diets are inversely linked epidemiologically to the incidence of colon cancer.131 This may be due to the fibre binding potential carcinogens, bile acids and toxins50 as well as an increased production of metabolites, through fermentation of short chain fatty acids, that have anti-neoplastic potential.88,132 Because psyllium is not easily digested higher up in the digestive tract it is subject to this fermentation in the colon therefore exerting its protective effect locally.

In vitro—Psyllium fibre protects colon epithelial cells, derived from people at high risk of developing this cancer, from tumour promoting metabolites like the bile acid deoxycholic acid.133 The short chain fatty acids help the proliferation and differentiation of colonocytes.133

In vivo—Using the seed fibre over a period of 3 months the level of the anticancer metabolite, butyrate, increased by 42% in people who had previously had colon cancer.134 Butyrate production does not persist when fibre use ceases.134

The effect of psyllium in patients with a history of adenomas showed that it may actually increase their recurrence especially if combined with a high calcium diet.135 Adenomas are associated with an increased risk of colon cancer.

Other

In vitro—The polysaccharides enhance proliferation of epithelial cells,136 reduce bacterial adherence and stimulate macrophage activity, they should therefore aid wound healing and may help limit scar formation.137

An extract and some fractions of the husk were inhibitory to Entamoeba spp.138

In vivo—The addition of psyllium and protein to the diet of hypertensive patients lowered their systolic blood pressure by around 6 mm Hg.139

Medicinal uses

Gastro-intestinal tract

Urinary tract

Externally

The seeds can be applied as a poultice to treat:

Pharmacy

Constipation 5–10 ml (1–2 teaspoons) followed by 250 ml (1 cup) of fluid per teaspoon. Treatment of IBS was effective at a daily dose of 20 g140
Hypercholesterolaemia a minimum of 7.2 g of husks per day has been recommended for reducing cardiovascular disease risk.108 Many of the studies used 10.5 g daily, as three divided doses of 3.5 g or two divided doses of 5.1 g, taken 15 minutes before meals. Relatively few side effects were recorded across the studies on cholesterol lowering (see under Precautions)88
Hyperglycaemia most studies used 5.1 g two or three times a day taken with or just prior to the meal.141 One study has reported that lowering of glycaemic index only occurs if psyllium is mixed with food.141

CONTRAINDICATIONS:—Stenoses of the gastro-intestinal tract, ileus, difficulty swallowing or diabetes mellitus where insulin adjustment is a problem.

Pharmacokinetics

In healthy people most of the mucilage has reached the caecum 4 hours after ingesting the husks.48

Precautions and/or safety

Use of husks and seeds does not alter blood biochemistry or most vitamin and mineral levels91,126 including co-ingested calcium.142 10.5 g of psyllium husks were administered daily for a year to a group of healthy people and their nutritional, haematological and biochemical status was checked at the end of this period with no significant changes found other than a small reduction in vitamin B12 levels. 143

Whilst most dietary fibres can alter/inhibit digestive enzyme activity psyllium was shown to either have no effect or to increase enzyme activity in vitro.144

Possible adverse effects include flatulence (may cause gas retention145 or a perception of flatulence due to bloating146), indigestion, nausea, bloating, retrosternal discomfort and vomiting.147 These minor side effects may be reduced by introducing fibre gradually, beginning with one dose a day.

There have been reported allergic reactions due to inhalation of psyllium powder148,149 and ingestion—possibly from proteins from the seed which are often present as contaminants of the husks.150,151 There have also been more serious cases of anaphylactic shock.152–154

Cases of oesophageal obstruction have been reported when treating constipation often due to insufficient water intake155–157 and in neurologically compromised patients.158,159 The Food and Drug Administration (America) has recently ruled that granular forms of psyllium are not safe and effective as a laxative for this reason. The ruling does not apply to Plantago psyllium in powder, tablet or wafer dosage forms.160 Other types of gastro-intestinal obstruction have also been reported.161–165

There is one case recorded of drug-induced reversible hepatitis to a commercial product containing the herb.166

Interactions

It is possible that the fibre can change the absorption and plasma half-life of drugs with which it is co-administered (based on animal data167) and it is therefore recommended that psyllium be used an hour after other drugs.

Because of its potential to alter blood sugar, psyllium could interfere with the drug treatment of diabetes.

Actual in vivo trials found no change in the absorption of either levothyroxine168 or digoxin169 when the drugs were used concurrently with the herb but there is an anecdotal report of it reducing the absorption of lithium salts.170

Concurrent use of psyllium and riboflavin was shown to reduce the apparent vitamin absorption.171

Historical uses

Genitourinary catarrh; as an expectorant, antitussive and diuretic. For rheumatic and gouty swellings.

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†From the Greek psylla—flea because the seeds are the shape and colour of fleas. Apothecaries called the seed Pulicariae from the Latin for flea.

†By making the stool softer and easier to pass.