MEADOWSWEET

Meadowsweet BP/EP, Filipendula BHP 1983 consists of the dried flowering tops of Filipendula ulmaria (L.) Maxim. [Spirea ulmaria L.], family Rosaceae.

This well-known perennial plant is found in wet meadows, marshes, by rivers, etc. throughout most of Europe, temperate Asia and as an escape in the eastern US and Canada. It is up to 120 cm in height with numerous radical longish petioled leaves. Each leaf is composed of up to five pairs of ovate serrated leaflets. Numerous aromatic cream-coloured flowers form irregular cymose panicles, which are particularly dense on the terminal branches of the leafy stems.

The commercial chopped drug occurs as clumps of broken leaflets dark green on the upper surface, paler and tormentose on the lower. Also brown fragmented flowers, unopened flower buds and small, more or less spirally twisted fruits containing brown seeds. Angular,greenish-brown longitudinally ridged hollow stems up to 5 mm in diameter constitute a considerable portion of the drug.

Among the complex mixture of structures in the powder the following can be noted: leaves and sepals having lower epidermis with slightly sinuous anticlinal walls, anomocytic stomata and cluster crystals of calcium oxalate up to 40 μm diameter in the mesophyll; papilose epidermis of petals; pollen grains with three pores and a smooth to slightly pitted exine; numerous trichomes, occasionally glandular with a one- to three-celled stalk and multicellular head with brown contents but principally clothing trichomes of various size, often twisted together; vascular tissue of the stem and veins.

Constituents

The BP/EP requires a minimum concentration of 0.1% for the steam volatile fraction of Meadowsweet; the flowers have recorded higher values. The major component of the oil (up to ca 70%) is salicylaldehyde (Fig. 21.1) together with methyl salicylate, benzaldehyde, benzyl alcohol, and smaller amounts of other components such as vanillin. In 1839, Löwingand and Weidmann, working on meadowsweet, were the first to report salicylic acid as a natural product. Other constituents of the drug are the phenolic glycosides gaultherin (Table 21.1) and spiraein (salicyl alcohol + primerose), various flavonoids, e.g. hyperoside (Fig. 21.18), tannins and mucilage.

Fig. 21.1 Simple phenolic compounds.

The pharmacopoeial TLC test for identity indicates the required presence of methyl salicylate and salicylaldehyde in the test sample. The permitted maximum for stems with a diameter greater than 5 mm is 5% and for foreign matter, 3%.

Oil of wintergreen

Natural oil of wintergreen was formerly obtained from the leaves of Gaultheria procumbens (Ericaceae), but is now distilled from the bark of Betula lenta (Betulaceae). Gaultheria oil of the Indian Pharmacopoeia is obtained from the fresh plant of Gaultheria fragrantissima and contains not less than 98% of esters calculated as methyl salicylate.

WILLOW BARK

Various species of Salix which include S. purpurea L., (purple willow) S. daphnoides Vill. and S. fragilis L. (crack willow) are sources of the official drug (BP/EP, BHP, ESCOP, Complete German Commission E). There are about 300 species of Salix showing much hybridization and unusual forms. They are distributed in all parts of the North Temperate Zone, the Arctic Zone and the South Temperate Zone. Identification can present difficulties. Species range from tall trees to tiny shrubs. The commercial drug is obtained principally from S.E. Europe but also from Britain and other European countries.

The commercial drug occurs as thin, channelled pieces of varying length, about 1.5 cm wide and 1.5 mm thick. It easily fractures longitudinally and, transversely, shows an inner inconspicuous fibrous fracture. The outer surface is brown, grey or greenish, glossy and smooth or dull and rugged; the inner surface is lightish brown and finely longitudinally striated. The powder is characterized by cork cells, parenchymatous cells containing cluster crystals of calcium oxalate and lignified fibre groups with crystal sheaths of calcium oxalate.

Willow bark is a source of salicin (Table 21.1), a phenolic glycoside now seldom used but generally regarded as the natural forerunner of aspirin. The composition of the glycoside mixture is variable in the bark depending on species, age of bark and time of collection. The latter is usually made in spring when the bark is easily removed from the branches. Other phenolic glycosides are salicortin (an ester of salicin), acetylated salicin (fragilin) and salicortin. Salicin is easy to prepare (see 15th edition of this book) and is a suitable compound with which to introduce students to this class of glycoside.

Flavonoids of the bark (to over 4%) include the 5- and 7-glucosides of naringenin, isoquercitrin and chalcone (see Fig. 21.18). Tannins are of the condensed types (q.v.).

The BP requires the dried drug to contain a minimum of 1.5% total salicylic acid derivatives, calculated as salicin. Liquid chromatography with spectrophotometric determination at 270 nm is used for the assay.

Willow is employed as an anti-inflammatory in the treatment of rheumatism, arthritis and muscular pains.

Black haw bark

The root bark of Viburnum prunifolium (Caprifoliaceae) was formerly official in most pharmacopoeias, but its use for dysmenorrhoea, threatened abortion and asthma has gradually decreased. It contains about 0.2% of salicin, volatile oil and isovaleric acid, tannin and resin.

HOPS

Hops are the dried strobiles of Humulus lupulus L. (Cannabinaceae). Only the pistillate plants are cultivated, large quantities being produced in England (particularly Kent), Germany, Belgium, France, Russia and California. The strobiles are collected, dried in kilns and pressed into bales known as ‘pockets’. They are sometimes exposed to the fumes of burning sulphur, which modifies the sulphur components already in the hops but which is said to stabilize the aroma and colour.

Hops are included in the EP, BP, BHP and in monographs of the British Herbal Compendium, ESCOP and German Commission E.

The hop strobiole consists of external and internal sessile bracts which overlap one another and enclose the ovary. Together they form a petiolate greenish-yellow inflorescence 2–5 cm in length. The odour is characteristically aromatic.

On the fruits and bases of the bracts are numerous shining glands. These, when separated, constitute the drug lupulin. The commercial product is generally very impure, owing to the fact that it is obtained by sieving the sweepings of the hop room floors. It occurs as a granular, reddish-brown powder with a characteristic odour and bitter aromatic taste.

The bracts and stipules of the hop contain tannin but the odour and taste of the drug are mainly due to the very complex secretion contained in the lupulin glands. On distillation the fruits yield 0.30–1.0% of an oil composed of well over 100 components and containing terpenes, sesquiterpenes including humulene (Fig. 21.3) and compounds such as 2-methyl-but-3-ene-2-ol and 3-methylbutanoic acid. The two latter, and related substances, increase significantly during processing of the fresh hops. The bitterness is due to crystalline phloroglucinol derivatives known as α-acids (e.g. humulone), β-acids (e.g. lupulone) and also about 10% of resins. 2,3,4-Trithiapentane, S-methylthio-2-methylbutanoate, S-methylthio-4-methyl-pentanoate and 4,5-epithiocaryophyllene have been isolated from the volatile oil of unsulphurated hops.

Fig. 21.3 Constituents of hops.

There has been considerable recent interest in the wide-ranging biological activities of the constituents of hops. Thus prenylated compounds such as xanthohumol and the recently isolated acylphloroglucinol-glucopyranosides have been variously reported to have cytotoxic effects on human cancer cell lines together with antiproliferative, antioxidant and oestrogenic properties. For details, see L. R. Chadwick et al., J. Nat. Prod., 2004, 67, 2024; G. Bohr et al., J. Nat. Prod. 2005, 68,1545. The mildly sedative properties of hops are ascribed, in part, to 2-methyl-3-buten-2-ol; their principal use is as an aromatic bitter in the preparation of beer.

Kamala

Kamala consists of the trichomes and glands separated from the fruits of Mallotus philippinensis (Euphorbiaceae), a tree found in India, Pakistan and the East Indies. It occurs as a dull reddish-brown powder without odour or taste. Under the microscope it is seen to consist of very characteristic globular glands containing red resin, and radiating groups of unicellular curved trichomes. It contains the anthelminthic phloroglucinol derivatives rottlerin and isorottlerin, resins and wax. It is used in India for the treatment of tapeworm infestation; also for treating poultry.

Tar (Pix Liquida)

Wood tar is known in commerce as Stockholm tar. It is prepared by the destructive distillation of various trees of the family Pinaceae. In addition to the tar, an aqueous distillate is obtained from which acetic acid, methyl alcohol and acetone are prepared. A residue of wood charcoal remains in the retorts. Wood tar is a blackish semiliquid with a characteristic odour and taste.

The constituents include the following phenols and phenolic ethers: phenol, C₆H₅OH; cresols, C₆H₄(CH₃)OH; methyl cresols; catechol or pyrocatechin, C₆H₄(OH)₂; guaiacol (methyl catechol) and its homologues. Also the hydrocarbons benzene, toluene (methylbenzene), xylenes (dimethylbenzenes), mesitylene and pseudocumene (trimethylbenzenes), styrene (phenylethylene), naphthalene (C₁₀H₈), retene (m-methylisopropylphenanthrene), chrysene (C₁₈H₁₂) and paraffins.

Pine tar is characterized by the large amount of guaiacol and its homologues which are present. Other tars, such as those of the birch and beech, show considerable differences in composition. Wood tar is acid in reaction, whereas coal tar, which is also official, is alkaline and in light petroleum gives a blue fluorescence. Creosote is obtained from wood tar by distillation. Tar is mainly used externally, in the form of ointment or tar parogen, as a stimulating antiseptic in certain skin diseases.

Wood tar, when shaken with water, gives an aqueous layer that is acid to litmus (cf. coal tar below) (BP test for identity).

COAL TAR

Coal tar is prepared by the destructive distillation of bituminous coal; it is a nearly black viscous liquid and when shaken with water gives an aqueous alkaline solution. A petroleum spirit extract has a blue fluorescence enhanced by UV light. The upper ash limit for the BP product is 2.0%.

Both coal tar and wood tar are used in the treatment of psoriasis.

VANILLA AND VANILLIN

Vanilla (Vanilla Pods) consists of the carefully cured fully grown but unripe fruits of Vanilla fragrans (Salis.) Ames (syn. V. planifolia Andrews) (Orchidaceae) (Mexican or Bourbon vanilla) and of V. tahitensis (Tahiti vanilla). The fruits of other species, such as V. pompona (West Indian vanilla), are also used but to a much more limited extent.

Vanilla fragrans is grown, in a semi-wild state, in the woods of eastern Mexico, its natural home. Vanilla is cultivated in Réunion (or Bourbon), Mauritius, Seychelles, Madagascar, Java, Ceylon, Tahiti, Guadeloupe, Martinique and Indonesia. China and India are now major producers and due to oversupply prices have fallen dramatically over the past few years.

Constituents

Green vanilla contains glycosides, namely glucovanillin (vanilloside) and glucovanillic alcohol. During the curing these are acted upon by an oxidizing and a hydrolysing enzyme which occur in all parts of the plant. Glucovanillic alcohol yields on hydrolysis glucose and vanillic alcohol; the latter compound is then by oxidation converted into vanillic aldehyde (vanillin). Glucovanillin, as its name implies, yields on hydrolysis glucose and vanillin (Fig. 21.4).

Fig. 21.4 Constituents of vanilla.

The three species given above differ in their relative contents of anisyl alcohol, anisaldehyde (also anisyl ethers and anisic acid esters), piperonal and p-hydroxybenzoic acid. These minor components, together with the two diastereoisomeric vitispiranes, add to the flavour of the pods.

BEARBERRY LEAVES

(Uva ursi)

Bearberry leaf EP/BP/BHP consists of the dried leaves of Arctostaphylos uva-ursi, Ericaceae; ESCOP and German Commission E monographs on the drug are also available.

A. uva-ursi is a small evergreen shrub found in central and northern Europe and in North America. The leaves are dark green to brownish-green, 2–3 cm long, obovate or spathulate, gradually narrowing to a very short petiole, apex obtuse or retuse. They are coriaceous in texture and almost glabrous. The upper surface is shiny and marked with sunken veinlets; the lower surface is lighter and marked with a network of dark veinlets. The drug is odourless but has an astringent and somewhat bitter taste.

Microscopical features include: an upper epidermis of polygonal cells with a thick cuticle; lower epidermis with anomocytic stomata and surrounded by 5–11 subsidiary cells; scars of trichome bases, occasional conical trichomes, crystal fibres.

Bearberry contains the glycosides arbutin (Table 21.1) and methylarbutin, about 6–7% of tannin, (+)-catechol, ursone and the flavone derivative quercetin. Some 14 phenolic acid constituents, including gallic and ellagic acids, have been recorded.

The pharmacopoeial drug is required to contain at least 7.0% of hydroquinone derivatives calculated as arbutin. These are assayed by liquid chromatography of an aqueous extract of the leaves with arbutin as a reference and absorbance measurement at 280 nm. The official TLC chromatographic test for identity distinguishes arbutin, gallic acid and hydroquinone. Bearberry is diuretic and astringent and during excretion it exerts an antiseptic action on the urinary tract.

Propolis or bee glue

This is the material with which the honey bee seals cracks and crevices, and varnishes surfaces within the hive. Its composition varies according to geographical source. It is collected by worker bees from the leaf buds and is enriched by wounded plant exudates such as mucilages, gums and resins; bee secretions and enzymes are then mixed in. Like honey, the composition varies according to geographical source.

Propolis has a long history, it being used by the Egyptians in the embalming process (antiputrefactive), by the Greeks and Romans in wound treatment (antiseptic), by the Incas (antipyretic) and by inclusion in the London pharmacopoeias of the 17th century. Today it is used by medical herbalists and has become a popular medicament (S. Castaldo and F. Capasso, Fitoterapia, 2002, 73, S1). It also features in apitherapy—an old tradition that has experienced a recent revival.

Over 160 compounds have been shown to be involved and one analysis gave phenolics (58%), beeswax (24%), flavonoids (6%), terpenes (0.5%), lipids and wax (8%) and bioelements, e.g. Mn, Cu, Zn (0.5%). In temperate regions of Europe the resinous coating of poplar buds (Populus nigra, P. italica, P. tremula) forms a major collection source for the bees and the natural phenolic content of the resin, e.g. esters of caffeic and ferulic acids, vanillin, eugenol, flavonoids, etc., can be used to identify the natural source.

Latterly there have been numerous reports concerning the analysis and biological activity of propolis originating from various regions and especially from Latin American countries. In these areas species of Araucaria (Araucariaceae), Baccharis (Compositae) and Clusia (Guttiferae) have been established as biological sources. In addition to the constituents listed previously, prenylated cinnamic acid and chromane derivatives, diterpenoid acids, lignans and components of the volatile oil have been identified.

Notwithstanding the differences in chemical composition of propolis depending on geographical source, a pronounced antibacterial property is common to all. In temperate regions flavonoid and phenolic esters have been shown to exert bacterial activity. New polyisoprenylated benzophenones have recently been reported as antibacterial agents in propolis of Venezuelan origin (B. Trusheva et al., Fitoterapia, 2004, 75, 683), and similar compounds (propolones) have been found in that of Cuban origin together with garcinelliptone and hyperibone (I. M. Hernández et al., J. Nat. Prod., 2005, 68, 931). Neoflavonoids with anti-nitric oxide production activity occur in propolis from Nepal (S. Awale et al., J. Nat. Prod., 2005, 68, 858).

Readers requiring further information on this interesting substance can refer to the references on p. 219 in the 15th edition of this book, and to Fitoterapia, Supplement 1, 2002, 73, S1–S64, devoted entirely to propolis; V. Bankova, J. Ethnopharmacol., 2005, 100, 114; Y. Lu et al., Fitoterapia, 2004, 75, 267.

CAPSICUM

The BP/EP drug (Chillies; Red Peppers) consists of the dried, ripe fruits of Capsicum annuum var. minimum (Miller) Heiser, and small-fruited varieties of C. frutescens L. (Solanaceae). In commerce the description given applies to various African commercial varieties (principally from Zimbabwe and Malawi) and these are sold in England as chillies, while the larger but less pungent Bombay and Natal fruits are known as capsicums. Very large Capsicum fruits, resembling tomatoes in texture and practically non-pungent, are widely grown in southern Europe as vegetables.

Constituents

In 1876, Thresh extracted the drug with petroleum, treated the extract with aqueous alkali, and by passing carbon dioxide through the alkaline liquid precipitated crystals of an intensely pungent compound, capsaicin. As may be inferred from the method of preparation, capsaicin is of phenolic nature.

The pungent phenolic fraction of capsicum also contains a proportion of 6,7-dihydrocapsaicin. The capsaicin content of fruits varies appreciably in a range up to 1.5% and is much influenced by environmental conditions and age of the fruit. It occurs principally in the dissepiments of the fruits—for example, entire fruit 0.49, pericarp 0.10, dissepiment 1.79, seed 0.07. The pungency of capsicum is not destroyed by treatment with alkalis (distinction from gingerol, which also contains the vanillyl group) but is destroyed by oxidation with potassium dichromate or permanganate. Chillies also contain ascorbic acid (0.1–0.5%), thiamine, red carotenoids such as capsanthin and capsorubin (see ‘Carotenoids’) and fixed oil (about 4–16%). They yield about 20–25% of alcoholic extract (capsicin) and about 5% (official limit 10.0%) of ash. Hungarian capsicums or ‘Paprika’ are derived from a mild race of C. annuum and are a convenient source of ascorbic acid. According to Bennett and Kirby, the pungent principle of C. annuum is composed of capsaicin 69%, dihydrocapsaicin 22%, nordihydrocapsaicin 7%, homocapsaicin (C₁₁ acid) 1% and homodihydrocapsaicin 1%. A number of minor components of this class have been recorded.

In a study of the water-soluble constituents of the fruits of three varieties of C. annuum, Izumitani et al. (Chem. Pharm. Bull., 1990, 38, 1299) isolated twelve novel acyclic glycosides (geranyllinalool derivatives) named capsianosides A–F (dimeric esters of acyclic diterpene glycosides) and capsianosides I–V (monomeric compounds of acyclic diterpene glycosides). Further capsianosides have now been reported by J.-H. Lee et al., (Chem. Pharm. Bull., 2006, 54, 1365). T. Ochi et al., (J. Nat. Prod., 2003, 66, 1094) record a dimeric capsaicin having almost the same antioxidant activity as capsaicin but with no pungent taste (Fig. 21.5).

Fig. 21.5 Some constituents of capsicum.

Hydrolysable tannins

These may be hydrolysed by acids or enzymes such as tannase. They are formed from several molecules of phenolic acids such as gallic and hexahydroxydiphenic acids which are united by ester linkages to a central glucose molecule. A simple tannin illustrating this point is one derived from a species of sumac (Rhus), with a possible structure as shown in Fig. 21.6. Like gallic acid their solutions turn blue with iron salts. They were formerly known as pyrogallol tannins, because on dry distillation gallic acid and similar components are converted into pyrogallol. Two principal types of hydrolysable tannins are gallitannins and ellagitannins which are, respectively, composed of gallic acid and hexahydroxy-diphenic acid units. Ellagic acid (the depside of gallic acid) can arise by lactonization of hexahydroxydiphenic acid during chemical hydrolysis of the tannin; thus, the term ellagitannin is a misnomer.

Fig. 21.6 Examples of hydrolysable tannins and their component acids.

Ellagitannins found in plants of medicinal interest, and for which structures have been elucidated include geraniin (Herb Robert and American cranesbill) and tellimagrandins 1 and 2 (Oak bark, Pomegranate and Meadowsweet); Fig. 21.6.

Modern methods of analysis have made considerable advances in the study of tannin chemistry of medicinal plants as evidenced by the work of Okuda on oriental drugs. In 1982 agromoniin, the first of a new class of oligomeric hydrolysable tannins was isolated from Agromonia. These tannins are composed of two, three or four monomeric units. Something less than 20 of these units including geraniin and tellimagrandins 1 and 2 are known to be involved in the production of over 150 compounds.

As an example, many plants of the Onagraceae e.g. Oenothera spp. contain in addition to tellimagrandin, the dimer oenothein B and trimer oenothein A; these macrocyclic ellagitannins are also produced in callus cultures of O. lacinata and are of interest for their anticancer and polygalacturonase-inhibiting properties (S. Taniguchi et al., Phytochemistry, 1998, 48, 981).

C-glucosidic ellagitannins are common in a number of families including the Myrtaceae, Hamamelidaceae, Punicaceae and Rosaceae and several have also been recorded as moieties of more than 10 oligomeric ellagitannins.

For an article on the classification of oligomeric hydrolysable tannins and the specificity of their occurrence in plants see Okuda et al., Phytochemistry, 1993, 32, 507.

In a series of enzymatic studies Gross and colleagues indicated the central position of β-D-glucogallin in the early stages of tannin synthesis in Quercus robur leaves. This compound appears to act as both donor and acceptor of the galloyl group in the enzymatic formation of 1,6-digalloyl-D-glucose; the responsible enzyme is β-glucogallin: β-glucogallin 6-O-galloyl-transferase.

The presumed immediate precursor of the two subclasses of hydrolysable tannins (gallotannins and ellagitannins) is 1,2,3,4,6-pentagalloylglucose, and in a continuation of their enzyme studies the above group have purified (×500) the enzyme responsible for the conversion of the precursor to the gallotannin 3-O-digalloyl-1,2,4,6-tetra-O-galloyl-β-D-glucose. The source of the enzyme was Rhus typhina (staghorn sumac) and its designation is β-glucogallin: 1,2,4,6-pentagalloyl-β-D-glucose galloyl-transferase (R. Niemetz and G. G. Gross, Phytochemistry, 1998, 49, 327).

Examples of drugs containing hydrolysable tannins are:

Gallitannins: rhubarb, cloves, red rose petals, bearberry leaves, Chinese galls, Turkish galls, hamamelis, chestnut and maple.

Ellagitannins: pomegranate rind, pomegranate bark, myrobalans, eucalyptus leaves, kousso, some Australian kinos, chestnut (Castanea spp.) and oak bark.

Condensed tannins (proanthocyanidins)

Unlike hydrolysable tannins, these are not readily hydrolysed to simpler molecules and they do not contain a sugar moiety. They are related to the flavonoid pigments and have polymeric flavan-3-ol structures. Catechins, which also occur with the tannins and flavan-3,4-diols (leucoanthocyanidins) are intermediates in the biosynthesis of the polymeric molecules. Stereochemical variations add to the variety of possible structures. Monomeric, dimeric and trimeric forms are illustrated in Fig. 21.7. Work by Japanese phytochemists has exploited modern techniques for separating and determining the structures of these oligomers and polymers including those of cassia bark, Cassia fistula, cinchona, Quercus and rhubarb.

Fig. 21.7 Structures associated with condensed tannins.

On treatment with acids or enzymes condensed tannis are converted into red insoluble compounds known as phlobaphenes. Phlobaphenes give the characteristic red colour to many drugs such as red cinchona bark, which contain these phlobatannins and their decomposition products. On dry distillation they yield catechol and these tannins are therefore sometimes called catechol tannins. Like catechol itself, their solutions turn green with ferric chloride.

Some drugs (e.g. tea, hamamelis leaves and hamamelis bark) contain both hydrolysable and condensed tannins. The following are rich in condensed tannins:

‘Complex tannins’

This term has been applied by Okuda to a newly-discovered group of tannins which are biosynthesized from both a hydrolysable tannin (mostly a C-glucoside ellagitannin) and a condensed tannin. The union occurs through a C–C bond between the C-1 of the glucose unit of the ellagitannin and the C-8 or C-6 of the flavan-3-ol derivative. The monomers are also involved in oligomer formation.

To date, complex tannins have not great relevance to mainstream pharmacognosy; monomers have been isolated from the Combretaceae, Fagaceae (Quercus, Castanea), Myrtaceae, Polygonaceae (Rheum) and Theaceae (Camellia). It is anticipated that many more compounds of this group will be discovered.

Pseudotannins

As already mentioned, pseudotannins are compounds of lower molecular weight than true tannins and they do not respond to the goldbeater’s skin test. Examples:

GALLS AND TANNIC ACID

Turkish galls (Turkey Galls; Galla) are vegetable growths formed on the young twigs of the dyer’s oak, Quercus infectoria (Fagaceae), as a result of the deposition of the eggs of the gall-wasp Adleria gallaetinctoriae.

The dyer’s oak is a small tree or shrub about 2 m high which is found in Turkey, Syria, Persia, Cyprus and Greece. Abnormal development of vegetable tissue round the larva is due to an enzyme-containing secretion, produced by the young insect after it has emerged from the egg, which by the rapid conversion of starch into sugar stimulates cell division. As starch disappears from the neighbourhood of the insect, shrinkage occurs and a central cavity is formed in which the insect passes through the larval and pupal stages. Finally, if the galls are not previously collected and dried, the mature insect or imago bores its way out of the gall and escapes. During these changes the colour of the gall passes from a bluish-grey through olive-green to almost white.

Galls are collected by the peasants of Turkey and Syria. After drying they are graded according to colour into three grades, blue, green and white, which are found on the London market.

HAMAMELIS LEAF

Hamamelis leaf (witch hazel leaves) consists of the dried leaves of Hamamelis virginiana L. (Hamamelidaceae), a shrub or small tree 2–5 m high, which is widely distributed in Canada and the USA. It is official in the BP/EP and is the subject of an ESCOP monograph.

TORMENTIL

There are over 300 spp. of Potentilla family Rosaceae of which several, including P. anserina, (silverweed), P. reptans (creeping cinquefoil) and P. erecta (common tormentil), find medicinal use. Tormentil BP/EP consists of the whole or cut dried rhizome, freed from roots of P. erecta (L.) Raeusch. (P. tormentilla Stokes). This perennial plant is widely spread throughout central and northern Europe, favouring the acidic soils of marshes, meadows, open woods and hills. Commercial supplies come from East European countries.

Plants are up to 30 cm tall with several loosely pilosed stems bearing leaves consisting of three- to five-toothed finely haired leaflets. Yellow flowers in loose terminal cymes have long pedicels and, unusually for the genus, four petals.

The rhizomes are dark brown on the outer corky layer and white on the inside when freshly broken, but turning red on exposure to the air. The chopped dried drug consists of hard pieces of rhizome with the remains of roots attached. Depressed pale scars from the stems are visible and some remains of stems in the form of fine, branching strands, less than 1 mm in diameter, may also be attached to the rhizome. The fracture is granular, odour faint but not unpleasant and the taste strongly astringent.

Characteristic features of the powder include brown cork cells, parenchymatous tissue containing tannin, sclerenchymatous tissues, vascular elements, starch in conglomerates or as single grains up to about 20 μm in length, and abundant cluster crystals of calcium oxalate up to about 50 μm in diameter.

HAWTHORN

The leaves, flowers and false fruits are all medicinally useful, the leaves and flowers being used principally for the preparation of infusions, etc. with the fruits employed in the manufacture of prepared medicaments. The dried false fruits of Crataegus monogyna and C. laevigata, family Rosaceae, together with their hybrids are official in the EP, BP and BHP; similarly the leaf and flower, for which there is also an ESCOP monograph.

The thorny, deciduous trees are native to Europe and have a long medical and ethnobotanical history. Commercial supplies of the dried fruits, required to contain not less than 1.0% procyanidins, originate from Eastern Europe.

AGRIMONY

Agrimony BP/EP, BHP family Rosaceae consists of the dried flowering tops of Agrimonia eupatoria L.

This erect, chalk-loving perennial herb is common throughout southern Europe and is indigenous to the British Isles, except for northern Scotland. Related species are found across North America. Hungary and Bulgaria are commercial suppliers of the drug.

The leaves are compound imparipinnate, with four to six opposite pairs of leaflets and a terminal leaflet. Larger leaflets are up to 6 cm in length with coarsely serrate or serrate–dentate margins, usually densely villous and often greyish on the lower surface. The golden flowers, 5–8 mm in diameter, are arranged spirally as terminal spikes. The pendulous fruits, 4–6 mm long, are deeply grooved with small projecting hooked bristles.

Characteristic microscopical features include stiff, thick-walled trichomes (500 μm) often with spiral thickenings and abundant clusters and prisms of calcium oxalate in the leaf mesophyll. Stomata are mainly of the anomocytic, occasionally anisocytic type. Pollen grains are ovoid to subspherical (up to 60 μm × 35 μm) with three pores and a smooth, thin exine.

The BP drug is required to contain a minimum of 2.0% tannins, expressed as pyrogallol when assayed by the official ‘determination of tannins in herbal drugs’. The TLC test of identification exploits the flavonoid content (rutin and isoquercitroside as test substances). Vitamins, triterpenes, volatile oil have also been reported as components of the drug.

Among other herbal uses, agrimony is employed as a mild astringent, internally and externally, against inflammation of the throat and for gastroenteritis.

ALCHEMILLA

The flowering and aerial parts of the lady’s mantle, Alchemilla xanthochlora (A. vulgaris sensu latiore), family Rosaceae, are described in the BP/EP and BHP 1996. The plant is widespread in Europe, North America and Asia; commercial supplies are obtained principally from Eastern Europe. In addition to the identification by macroscopic and microscopic characters the pharmacopoeias include thin-layer chromatographic tests providing characteristic fluorescent zones.

The BP/EP drug is required to contain not less than 6.0% of tannins expressed as pyrogallol when determined by the official method (cf. Hamamelis and Rhatany). The characterized ellagitannins are pedunculagin and the dimeric alchemillin. Other constituents are flavonoids, quercetin 3-O-β-D-glucoside having been isolated as the major flavonoid in leaves of French origin.

Alchemilla acts as an astringent against bleeding and diarrhoea and has a long tradition of use for gynaecological conditions such as menorrhagia.

RHATANY

Rhatany of the BP and EP (Krameria) is the dried root of Krameria triandra (Krameriaceae, a small family related to the Leguminosae), a small shrub with decumbent branches about 1 m long. The drug is collected in Bolivia and Peru and is known in commerce as Peruvian rhatany.

The root has a knotty crown several centimetres in diameter and gives off numerous branch roots some of which attain a length of 60 cm. The roots are nearly cylindrical and are covered with a reddish-brown cork, which is scaly except in very young roots. A transverse section shows a reddish-brown bark which occupies about one-third of the radius and encloses a yellowish, finely radiate wood. A small, deeply coloured heartwood is sometimes present in the larger species. The bark readily separates from the wood. The former is astringent but the latter almost tasteless.

The tannins of krameria root (krameria-tannic acid) are entirely of the condensed (proanthocyanidin) type having a ‘polymeric’ flavin-3-ol structure. In this instance there is a procyanidin:propelargonidin ratio of 35:65 as determined by acid hydrolysis. Astringency of the root is due to compounds with a degree of polymerization of more than five. (For further details see E. Scholz and H. Rimpler, Planta Med., 1989, 55, 379). A phlobaphene (krameria-red), starch and calcium oxalate are also present. Stahl and Ittel (1981) reported the isolation of two benzofuran derivatives, ratanhiaphenols I and II, from the root. Both compounds are effective u.v. light filters and could be useful in sun-protection preparations. The BP and EP include an assay for tannins (polyphenols) of not less than 5.0% based on the colour reaction involving alkaline sodium phosphomolybdotungstate (absorbance measured at 760 nm). Polyphenols not adsorbed by hide powder, also determined with the same reagent, are excluded from the calculation.

The drug is used as an astringent and the significant antimicrobial activity of the extract gives rational support for its use in mouth and throat infections.

Pomegranate rind

The pomegranate fruit is one of the oldest known to man and has featured in mythology, and as a food and medicine from ancient civilizations of the Middle East to its present wide cultivation in India and surrounding countries, Turkey, southern Europe and California.

Pomegranate rind consists of the dried pericarp of the fruit of Punica granatum (Punicaceae). It occurs in thin, curved pieces about 1.5 mm thick, some of which bear the remains of the woody calyx or a scar left by the stalk. The outer surface is brownish-yellow or reddish. The inner surface bears impressions left by the seeds. Pomegranate rind, used in India as a herbal remedy for non-specific diarrhoea, is very astringent and contains about 28% of tannin (ellagitannins) and colouring matters. It should be distinguished from the root bark, which contains alkaloids.

For a discussion of the biochemistry, health effects, commercialization, plant growth and improvement of the pomegranate fruit, see N. P. Seeram et al. (eds), R. Hardman (series ed.) 2006 Medicinal and aromatic plants – industrial profiles, Vol 43. Pomegranate. CRC Press, Taylor and Francis Group. Boca Raton, FL., 244 pp.

Aspidosperma barks

The bark of Aspidosperma quebracho-blanco (Apocynaceae), which is used as a tanning material, was formerly official in several pharmacopoeias.

Myrobalans

Myrobalans are the dried fruits of Terminalia chebula (Combretaceae), a tree common in India. The immature fruits are black, ovoid and about 1–3 cm long. They contain about 20–40% of tannin, β-sitosterol, anthraquinones and a fixed oil containing principally esters of palmitic, oleic and linoleic acids. The tannin and anthraquinone constituents make the drug both astringent and cathartic in action. Microbiological tests support the Indian use of an aqueous extract of the fruit as an anticaries agent (A. G. Jagtap and S. G. Karkera, J. Ethnopharmacology, 1999, 68, 299).

CATECHU

Gambir or pale catechu of the BP 1989; BP (Veterinary), 2007 is a dried, aqueous extract prepared from the leaves and young twigs of a climbing shrub, Uncaria gambir (Rubiaceae). It must be carefully distinguished from black catechu or cutch. The plant is a native of Malaya and it is largely cultivated for the production of the drug in Indonesia and Malaya for marketing through Singapore.

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