support the claims for efficacy made by traditional medical systems. The
reason is that, in African TMP, almost no organic solvents are used and
whole plant products or extracts are administered. Furthermore, it is being
increasingly recognised that the efficacy of whole plant extracts may be
the product of a complex balance between various secondary chemicals
involving synergistic and solubilising effects, as well as a possible mitiga-
tion of toxicity.^53 Attempts to isolate one or two ‘actives’ from traditionally
used plants have frequently been disappointing, in that individual
compounds have exhibited a loss of activity and/or increased toxicity or
presented difficulties in formulation.^54 Many TM plant species have defied
identification of individual ‘actives’ or have been shown to contain
mixtures of therapeutically active secondary metabolites that are ubiqui-
tous in the plant kingdom, e.g. tannins, flavonoids and oleanolic acid.55,56
A further drawback associated with bioassay-guided fractionation lies in
the fact that it has permitted the patenting of isolated molecules for partic-
ular therapeutic applications, thus bypassing the need for recognition of IP
rights in indigenous knowledge. This legally permissible but ethically
questionable practice will persist until such time as all African states have
adequate legislation in place for protection of traditional medical systems
and practitioners.
With respect to the validation of efficacy of (as opposed to new drug
discovery from) African TMs, in vitro assays are widely used, mainly on
account of their greater affordability when compared with in vivo models.
The most common approach is to prepare plant extracts of varying polarity
and test these separately for activity, often using a single in vitro bioassay.
There are some flaws in this approach, namely that aqueous infusions are
used in African traditional medical practice and, second, that a single
bioassay is probably insufficient to demonstrate activity.^57 Consequently,
much of the current scientific literature purporting to validate the claims
made by TMs does not in fact do so. There have been some studies using
traditional dosage forms,58–60but few that take into account the effects of
genetic or environmental variability on plant secondary chemistry/bioac-
tivity. Box 5.2 lists some recent publications dealing with ethnopharmaco-
logical screening programmes for antimalarial/antiplasmodial activity,
carried out in various African countries.
A different approach has been taken by the phytomedicines industry,
which utilises whole plant products or extracts of plant species used as tradi-
tional medicines. Examples of successful introductions of African TMs to this
sector of the market are given in Table 5.4 (see also Stewart61,62).
Safety
Much benefit is to be gained from the rational use of traditional medicines
within the formal healthcare system in Africa.^31 For this reason there is a need
Traditional medical practice in Africa | 105