14 - Neurotoxicity and Neuroprotective Effects of African Medicinal Plants

Abstract

The central nervous system (CNS) is an important sanctuary site and it is protected not only by the blood–brain barrier but also by many other barriers. These same barriers regulate brain homeostasis and the transport of endogenous and exogenous compounds by controlling their selective and specific uptake, efflux, and metabolism in the brain. Unfortunately, potential drugs for the treatment of most brain diseases often are not able to cross these barriers, and even those that are able to cross these barriers could be inactivated by several metabolic pathways. A search for novel pharmacotherapy from medicinal plants for neurotoxic diseases has progressed significantly in the past decade. We found that the studies demonstrating either stimulating or depressive activity on the CNS have been in certain classes of compounds, namely, alkaloids, amino acids, and phenolic and polyphenolic compounds. However, the correlation between classes of compounds and bioactivity at the CNS was not linear, and the search for compounds with this kind of bioactivity was not restricted to a particular class and did not exclude other classes of compounds. The initial purpose of this review was to screen African medicinal plants with neurotoxic and/or neuroprotective activities, in particular those that have been studied and that have molecular mechanisms whose active constituents responsible for the activity remain to be identified. Forty individual medicinal plants reviewed were classified as neurotoxic and/or neuroprotective herbs.