A largely tropical family of trees and shrubs with resinous tissues, probably best known through the cashew nut tree (Anacardium occidentale) and the mango (Mangifera indica). Both these species have unifoliolate leaves, whereas compound imparipinnate leaves are typical of the indigenous members of the family, with the exception of Heeria, with two widespread savanna species, one a suffrutex, the other woody. Heeria (now Ozoroa) also has opposite or whorled leaves, while alternate (and exstipulate) ones are otherwise typical of the family. Terminal and/or axillary inflorescences, of small, pale three- to five- part flowers, and resinous drupes with a single stone are characteristic of the whole family.

Nothospondias is now placed in the Simaroubaceae. There are new illustrations of Antrocaryon micraster, Lannea schimperi and Pseudospondias microcarpa (Kokwaro, 1986).

Introduced species include two tropical American species of pepper tree (Schinus spp.).

Flowers ⊕ ♂, ♀ or on the same or different plants, 3–5-part; both mango and cashew nut (also Fegimanra) have .1. flowers, having often only 1 fertile stamen and having a single carpel. Most genera are polygamous as described above, but a few (Haemostaphis etc.) show dioecy. K small, 4–5 or (4–5). C4–5, mostly imbricate; in 4-part perianths, the sepals are orthogonal, the petals diagonal. Only Haematostaphis has 3-part flowers.

A large and diverse temperate and tropical family, well represented in West Africa by woody species in both forest and savanna.

Members of the family may be recognised by their alternate, simple, mostly stipulate, pinnately nerved leaves, and by the frequent presence of latex, glands, stellate and peltate scales. Flowers are small, ♂ or ♀, usually five-part and in inflorescences which are often axillary and condensed. The ♀ flowers usually have a three-celled ovary forming a three-lobed fruit with one or two seeds in each cell. Casearia (now Keayodendron) bridelioides has been transferred from the Samydaceae, which, in turn, is now joined with the Flacourtiaceae.

Species introduced for decorative purposes from America include poinsettia (Euphorbia pulcherrima), sandbox tree (Hum crepitans) and three species of jatropha. Snow bush (Breynia nivosa, now B. disticha var. disticha f. nivosa (Radcliffe- Smith, 1980) and croton (Codiaeum variegatum) have been introduced from Polynesia.

Some Euphorbias are recognisable at a distance, being shrubs or trees with fleshy, often angular, branches without leaves, which are minute and soon fall, but sometimes with spines. These c. 10 species occur in drier savannas, on inselbergs and sometimes as hedges (Marnier-Lapostolle, 1966; Rauh, Loffler & Uhlarz, 1969). Both these and the herbaceous species, e.g. E. glaucophylla on the shore, have latex and possess distinctive inflorescences (pseudanthia, cyathia). Similar inflorescences are seen in Elaeophorbia, of which there are two species of forest trees with fleshy angular branches, fleshy leaves and paired spines.

A small, mainly northern hemisphere family of trees, represented by only four genera in West Africa, all of them also present in a large part of the rest of tropical Africa. Only two species extend to Gambia. No introductions have been made.

Members of the family may be recognised by their simple, alternate stipulate leaves which are ± asymmetrical, pinnately nerved or three-nerved at the base. Flowers are very small, apetalous, ♂, ♀ or, in small axillary inflorescences. The two styles persist on the fruit whether this is a samara or a drupe.

Chaetacme aristata, a small southern savanna tree (Côte d'lvoire eastwards), is readily recognisable by the nodal prickles accompanying the leaf and axillary branch. Its dark-green leathery leaves end in a tiny spine, the produced midrib, and the large stipular hood leaves an encircling scar on the main axis, cf. Chapter 17, Moraceae.

Flowers ⊕ ♂, ♀ or, nearly always monoecious, 4–8 part. K(4–5–8) (free in Celtis), imbricate in Celtis and Holoptelea and ♂ and flowers of Trema and Chaetacme, valvate with the margins folded in (induplicate-valvate) in ♂ flowers of Trema and Chaetacme. CO. A as many as, and opposite, the sepals, episepalous, introrse (except Celtis). G(2) 2-celled (1-celled by abortion), with an apical ovule per cell; the 2 styles are ± branched, divergent, in the adaxial–abaxial plane of the flower, ± a pistillode in – flowers.

The second largest family of monocotyledons on a worldwide basis, but the first in importance both ecologically and economically, dominating all the ‘grasslands’ of the world and providing the grain and fodder which are staples of diet for both man and animals. Wheat, rice, maize and guinea corn are reported to cover half the world's land under food crops.

Grasses are annual or perennial rosette herbs, occurring in every kind of habitat. The long-lived bamboos are lignified and of tree-like dimensions, but there are quite a number of species, even annual ones, which reach 5 m or more in height and have cane-like stems. In habit, though plentifully branched, grasses may be compact and upright (tussock-forming), or trailing, creeping or decumbent, or extended by means of axillary shoots, which form stolons above ground or rhizomes underground. Descoings (1972) distinguishes five habits. Annuals lack stolons and rhizomes, but perennials may adopt any of these habits. New axillary shoots may be called tillers, and flowering shoots are known as culms, but all aerial shoots are basally branched and have a limited life span. Growth is sympodial and non-flowering shoots are relatively short lived.

The leaf blade, generally linear to lanceolate in outline, arises from an open sheath which encircles the stem and younger leaves closely. Venation is always parallel (convergent), the wider leaves appearing Commelina like.

Annual or perennial herbs, creeping or with taproots, mostly weeds of disturbed ground. Many species are pantropical or almost cosmopolitan in distribution, often by introduction.

Members of the family may be recognised (in 10/14 genera) by their opposite leaves, which are also simple and exstipulate, and condensed, erect, leafless racemose inflorescences (often spikes or clusters) with dry bracts and bracteoles, of minute apetalous flowers, each with a dry, often coloured calyx. The fruit is a utricle (an inflated achene, but see Chapter 39, Cyperaceae), which may, however, dehisce.

Introduced cultivated ornamentals include bachelor's button (Gomphrena globosa), cockscomb (Celosia argentea f. cristata), love-lies-bleeding (Amaranthus sp., see below) and Alternanthera (now tenella var.) bettzickiana.

There are very few climbers in the family and Sericostachys scandens, in the forests of southern Nigeria and Cameroun, is the only ± woody one. It has opposite leaves and large inflorescences, each unit of which is composed of one fertile and two (to three) sterile flowers. These latter develop white feathery hairs as the fruit ripens, and the infructescences are very striking.

Two more species are distinctive by both habit and habitat. Centrostachys aquatica, the only species in its genus and the only aquatic species in the family, has occasionally been collected along the southern border of the Sahara, to where its North African distribution extends. It has grooved floating stems rooting at the lower nodes and bearing opposite leaves, and flower spikes up to 30 cm long.

A large family, mainly of herbs and undershrubs in the tropics and subtropics, and particularly prominent in West Africa in forest undergrowth. Members of the family have opposite exstipulate leaves and lack latex. The leaves are generally shortly petiolate or sessile, and long-cuneate. The inflorescences are often conspicuous; either dense cone-like spikes with prominent overlapping, sometimes forked (or papery – Rungia), bracts from between which the flowers appear (Sell, 1969b), or lax and panicle like. The flowers are zygomorphic, with two or four stamens and a two-celled ovary developing into a characteristic capsule.

Introduced species occur as a rule only in gardens. The most prominent are the Indian Thunbergia grandiflora and T. laurifolia, with blue flowers (the former sometimes with white flowers), and T. alata, with winged petioles and yellow-to-reddish flowers with a dark ‘eye’. Two Barleria spp. have also been introduced.

Several genera contain only, or at least some, prickly species, the prickles often needle like. Crossandra, with prickle-edged bracts and pale flowers, and Acanthus, with prickly leaves as well, occur in forest, while Diclipera verticillata (also in Gambia) is a red-flowered savanna herb, the only one in the genus with a spine at the tip of each bracteole.

Lepidagathis collina is a yellow-flowered savanna herb which can grow as a pyrophyte. When it does so, its globular inflorescences resemble burrs, up to 4 cm Ø, the needle-like tips of the bracts (there are no bracteoles) sticking out all round.

A cosmopolitan family of perennials, mainly twiners and trailers, and often with tuberous roots or roots which readily produce adventitious buds. There are few annual, or erect, or woody species in West Africa. Irvine (1961) named only the liane genera Bonamia and Calycobolus as being woody, while Ipomoea verbascoides is an undershrub which might be thought so. Two introduced species are small trees, but these are seldom seen.

Other introduced species include about one-third of the remaining West African Ipomoea spp., e.g. I. alba, moonflower, which now occurs naturally in regrowth, but is often seen in gardens; another white-flowered climber, with winged pedicels, peduncles and older stems, Operculina macrocarpa, is recorded near the coasts of Ghana and Togo. Most introduced species are native to the Americas, including Merremia dissecta, the flowers of which are white with a purple throat opening in the evenings.

Members of the family may be recognised by their alternate, simple exstipulate leaves, which are sometimes digitately lobed, though rarely compound, and latex may be present. The flowers are distinctive, with a funnel-shaped or tubular corolla, often with at most small free lobes but with strongly marked Λ- shaped ribs, pleated and sometimes twisted as well in the bud, usually in some form of cyme. The fruit is generally a small two-celled capsule with four seeds, often surrounded by a persistent calyx.

A family of tropical and subtropical trees, shrubs and tendril lianes with, in West Africa, three species of these last representing large American genera – Cardiospermum spp. (balloon vines) and Paullinia pinnata.

Members of the family may be recognised by their alternate, compound pinnate leaves with conduplicate leaflets, and cymose spike or panicle-like inflorescences of minute, pale, apparently flowers. The petals bear scales or hairs on their inner faces, and there is an annular extrastaminal disc, or the disc or disc glands stand to one side of the stamens and pistil. The fruits are often three-valved capsules, with a single arilloid seed in each cell. Tissues are generally soapy when crushed in water.

The climbers have paired inflorescence tendrils and imparipinnate stipulate leaves, while the trees and shrubs have paripinnate exstipulate leaves, in which the rachis is often slightly prolonged. There is rarely only one pair of such leaflets (Aphania). The leaflets commonly decrease in size towards the base of the leaf, and the lowest pair may arise next to the axil (the leaf being ± sessile), and form pseudostipules (Eriocoelum, Blighia, compare Bignoniaceae).

There are 1–3-foliolate leaves in the genus Allophylus and 1-foliolate leaves only in Dodonaea viscosa, in both cases the leaves being exstipulate. D. viscosa is a glandular sea coast shrub with ⊕ apetalous four-part flowers.

The habit of a small erect palm is characteristic of some under-storey species of Chytranthus, Deinbollia and of Radlkofera calodendron.

Although there are only five genera in West Africa, three of them are important ecologically. These are trees and shrubs, Ouratea being a large genus (of c. 40 species in West Africa), containing, on a pantropical basis, half the species of the family (c. 300).

Members of the family may be recognised by their alternate, simple, stipulate leaves with prominent, numerous pinnate veins, shallow conspicuous white or yellow flowers (with 10 to numerous stamens) in racemose inflorescences, and by their fruits (see below).

Fleurydora felicis is endemic to West Africa and confined, so far as is known, to Guinée, where it grows as a yellow-flowered shrub or small tree among rocks. The only West African herb of the family, Sauvagesia erecta, is, however, widespread in wet places (also in Gambia), and has solitary, axillary white-to-pink flowers.

Flowers ⊕ 5-part. K5, coloured and/or persistent (caducous in Fleurydora). C5 (sometimes joined basally, Ouratea), contorted (valvate in Sauvagesia). A5 (Fleurydora and Sauvagesia), or 10 (Ouratea), alternating with the petals, or numerous (Lophira and Ochna); the filaments persistent, anthers opening by slits (terminal pores in Lophira, some Ochna spp., Ouratea, Fleurydora). G(2) (Lophira), (3) (Sauvagesia) or (5), uncommonly to (10), deeply lobed in Ochna and Ouratea with a gynobasic style; 1-celled in Lophira (with an intrusive basal placenta with several ovules) and in Sauvagesia with intrusive parietal placentae above, axile placentae below; 5–10-celled otherwise, very deeply lobed with a single basal ovule per cell in Ochna and Ouratea (several axile ovules in Fleurydora).

Plants and herbs have been used by man to cure disease and heal injuries since time immemorial. In recent years, renewed interest has been shown in the use of medicinal plants, and scientific studies are beginning to explain some of the curative phenomena associated with traditional herbal remedies. There has also been growing awareness by governments, and the scientific and medical communities, of the importance of medicinal plants in health care systems in many developing countries. This has led the World Health Organization to develop an international programme which will, inter alia, review available scientific data relating to the efficacy of medicinal plants in the treatment of specific conditions and diseases. A major task therefore will be to identify those plants suitable for use in primary health care, and to identify simple and/or intermediate technology that will produce enough drugs and therapeutic agents at low cost.

This work presents clear and concise scientific data on the pharmacology of West African plants and extends our knowledge of medicinal plants in West Africa. It will be of particular value to those interested in specific drug applications and will further encourage research into local herbs which in its turn will generate technology locally; this is more reliable and more relevant than introduced technology.

The flora of tropical West Africa has for centuries provided a wealth of material for healing purposes, and its further investigation presents a challenge to scientists who seek to contribute to the search to find new means of alleviating suffering and disease.

In 1975 I began to be interested in the study of the active principles of African medicinal plants and searched for relevant literature. At the time I was particularly interested in receiving more information on West African plants as we were developing experimental work in collaboration with the Chemistry Department of the Nigerian University of Nsukka and I became aware of the great difficulty in finding fairly reliable documentation even on some of the best-known traditional herbal remedies.

Factors which may account for this are that the local uses were very numerous and often differed from one tribe, village or healer to another. Also, not only did superstition play an important part (often both magical purposes and empirical beliefs were attributed to the plants) but purgatives, diuretics and emetics were often used to chase the evil influences the people did not understand.

The patient work of some distinguished scholars working in the field in Africa provided an important contribution to our acquisition of knowledge on the traditional uses but only a few publications gave a more selective view on the subject. Among these one of the most relevant to me was the book of Dr Bep Oliver (Oliver-Bever), Medicinal Plants in Nigeria. She selected uses which were confirmed by the use of the same plants as cures by primitive populations in other parts of the world with similar climate, and also those which were likely to have real therapeutic value from a consideration of the then known chemical and pharmacological information.

Introduction: the action of plants on hormone secretion in Man

A number of plant constituents can act as a substitute for natural hormones in cases of hormone deficiency. Some of these constituents have been found to be chemically identical with the natural hormone (e.g. oestrone in the kernels of date and oil palm). Other plant components have a structural similarity to the hormone (e.g. Funtumia and Holarrhena alkaloids and corticosteroids). Others again have an entirely different chemical structure (e.g. coumestans and isoflavones with oestrogenic action). All these constituents can act as a substitute for hormones and replace them in their biological functions.

Plant components often have an indirect action on the secretion of certain hormones by stimulating or inhibiting other areas like the hypothalamus and the pituitary gland which can control the function of most other glands (e.g. gonadotrophic, thyrotrophic and corticotrophic action). (For more details see Plants acting on sex hormones.) However, great precaution should be taken in using the hypothalamus–pituitary axis as a narrow interrelationship exists and often hormonal or pharmacological actions other than those desired can be obtained (Bianchi, 1962; Goodman and Gilman, 1976). Thus stimulation of lactation has been obtained with dried thyroid gland or thyroxine (Robinson, 1947; Naish, 1954), no doubt through indirect action via the pituitary gland and an impairment of the pituitary adrenal response to acute stress is observed in alloxan diabetes (Kraus, 1949).

Sex hormones

Female sex hormones

Oestrogens are the hormones concerned with the maturation of the female genital tract, the development of the secondary sexual characteristics and bone formation. The main oestrogens, oestradiol and oestrone, are secreted by the theca interna and appear in the fluid of the Graafian Follicles. Oestrogens are also secreted by the placenta and to a much lesser degree by the adrenal cortex. They are rapidly metabolized in the liver.

Progesterone is the hormone concerned with the maintenance of pregnancy. It is secreted by the corpus luteum and acts only on tissues formerly sensitized by oestrogens. It inhibits ovulation during pregnancy, depresses the action of oestrogens and produces further development of the breasts. It also plays a role in the development of the placenta and depresses uterine contractility.

The production of steroid hormones is controlled by the pituitary gonadotrophins (follicle-stimulating and luteinizing hormones). In large doses oestrogens can depress the gonadotrophic and lactogenic activities of the anterior pituitary gland. Because of their rapid metabolism by the liver, oral administration of the natural oestrogens is less effective than parenteral administration, with the possible exception of oestriol, which is claimed to be as potent when given orally as when given by injection.

The oestrogens are used to treat menopausal disturbances and cases of dysmenorrhoea and menorrhagia. Progesterone is used chiefly in the treatment of functional uterine haemorrhagia.

Insulin, a hormone secreted by the β-cells of the Islets of Langerhans in the pancreas, is of utmost importance for the correct metabolism of carbohydrates and fats. It induces the oxidative breakdown of glucose, has a stimulating effect on the synthesis of liver glycogen from glucose and inhibits the formation of liver glycogen from protein and fat.

Diabetes, a condition characterized by hyperglycaemia, is caused by insufficient secretion of insulin or to insufficiency of its peripheral efficacy. Excess of insulin leads to hypoglycaemia; this is easily counteracted if dextrose or a few lumps of sugar are taken at once.

Modern investigations into the biochemistry of diabetes show that its causes and the sites of intervention in the biochemical processes are diverse. Somatostatin, the pituitary and sex hormones, corticosteroids, prostaglandins and vascular modifications of the pancreas can all be involved, together with a straightforward inadequacy in insulin production (Randle et al., 1963; Gupta et al., 1966; Burkhard et al., 1968).

A number of plants have constituents which have antidiabetic properties when taken orally (Oliver-Bever and Zahnd, 1979). There is great diversity in the nature and action of these constituents, but a number of them do seem to belong to certain chemical groups, such as sitosterol glycosides, alkaloids, sulphur oils and flavonoids, and in this chapter I have assembled the plants described into a few groups based on their possible active chemical constituents while at the same time taking into consideration their relation to, or identity with, hypoglycaemic plant constituents found elsewhere.

This book is a sequel to the monograph Medicinal Plants in Nigeria, written in 1960 (Oliver, 1960), which was a critical survey of the scattered information available about drug plants found in Nigeria; it suggested a first choice of the plant material which seemed potentially most important, and made suggestions concerning points requiring further scientific investigation (constituents, pharmacology, etc.).

As medical science develops and becomes more organized in the West African countries, the time would seem to have come to reassemble and update our knowledge of the subject and extend it to the whole of tropical West Africa. Furthermore, greater importance is now being attached to the use of locally available medicines as a means of reducing reliance on expensive imported drugs.

Since the first book appeared, a number of papers dealing with the chemical analysis, pharmacology and clinical action of West African plants have been published. Supplementary information now available about individual plants will be included here, and the range of plants considered can thus be more selective. This time an attempt is made to classify the drugs according to their established or possible medical uses, this being the best way of rapidly assessing the medical interest of any particular drug.

The value of a drug will depend on several factors:

1. (1) whether it is the only drug, or one of the few drugs, used in the treatment of a disease;

2. (2) whether the disease in the treatment of which it is used is a common one;

3. […]