Introduction - African Medicinal Plants - page 2

The ancient African healers had an elaborate materia medica, which consisted of mixtures of
various herbs, animal parts, minerals, and clays. The Ebers Papyrus, one of the oldest in medical
literature, listed several recipes used by ancient African healers. The list, however, was dominated
by numerous food plants, in keeping with the belief at that time that “every disease to which men are
liable is occasioned by the substances whereon they feed” (p. 42). 3 Even today, there is no clear dis-
tinction in traditional African medicine regarding when an herb ceases to be a health food and when
it becomes a medicine. In traditional African medicine, many food plants are used for therapeutic
purposes, and medicines are not viewed as “necessary poisons.” This is in contrast to Western
orthodox medicine, in which drugs are seen as poisons that in low doses may cure diseases. One of
the most unfortunate ironies of herbal medical practice is that while African medicine consists pri-
marily of herbs and health foods, modern herbal producers and phytopharmaceutical manufacturers
seldom, if ever, include African medicinal plants in their lists. But, that is beginning to change with
the advent of “nutraceuticals” or dietary supplements in the Western system of medicine.
African materia medica do not consist of dietetics alone, but include many potent herbs. Few
African healing herbs are recognized in modern pharmacopoeias; the list includes calabar bean
(Physostigma venenosum) , Strophanthus , areca nuts, kino, Salix , kola, the African periwinkle
(Catharanthus roseus), and the devil's claw (Harpagophytum procumbens). It is interesting to
note that, in several instances, there are African varieties of many “official” drugs. The African
Rauvolfia vomitoria, for example, has a higher content of the antihypertensive alkaloid reserpine
and the antiarrythmic drug ajmaline than the better-known species of the genus Rauvolfia. . Another
example is the willow plant, Salix capensis, which has been used in southeastern Africa for centu-
ries as a painkiller and antipyretic; it is known to contain esters of salicylic acid, a compound whose
acetylated form is the universal analgesic, aspirin. The ginger cultivated in Nigeria is valued by
consumers more than the Asian and Caribbean varieties. Although there are many research publica-
tions available on the constituents and biological activity of medicinal plants from Africa, the devel-
opment of therapeutic agents from African medicinal plants has remained a somewhat neglected
subject. The study of African medicinal plants also has not been taken as seriously or documented
as fully as in other traditional societies, such as the Indian and Chinese. Our knowledge of African
medicinal plants is rather limited. The little available information is often fragmented, and most
African medicinal legends have become distorted by several centuries of continuous waves of inva-
sion and conquest of various parts of Africa.
The documentation of medicinal uses of African plants is becoming increasingly urgent because
of the rapid loss of the natural habitat of some of these plants due to anthropogenic activities. The
continent is estimated to have about 216,634,000 hectares of closed forest areas with a calculated
annual loss of about 1% due to deforestation; many of the medicinal plants become extinct before
they are even documented. Africa has one of the highest rates of deforestation in the world; for
example, Cote d'Ivoire and Nigeria have 6.5% and 5.0% deforestation per year, respectively; the
global rate is 0.6%. Habitat conversion threatens not only the loss of plant resources but also tra-
ditional community life and cultural diversity and the accompanying knowledge of the medicinal
value of several endemic species. The vegetation of Africa can be classified into a number of phyto-
choria, that is, regions within which a substantial proportion of the plants are endemic, following the
scheme proposed by White. 4 These include (1) Mediterranean North Africa, (2) the cape region of
South Africa, (3) tropical Africa, and (4) Madagascar. Within tropical Africa, the major ecosystems
are (1) forests; (2) seasonal tropical vegetation (which consists of woodland, bushland and thicket,
grassland, shrublands); (3) deserts; (4) montane and afroalpine ecosystems; (5) wetlands; (6) lakes;
and (7) coastal vegetation. The majority of the plants found in Africa are endemic to the continent,
with the Republic of Madagascar having the highest rate of endemism, 82%. The island contains
over 12,000 species in its original forest areas, and 4900 of these species are found only on that
island. 5 There is therefore an urgent need to document not only the uses but also the constituents
and pharmacological activity of these plants. Over 5000 plants are known to be used for medicinal