Herbal neurotoxicity: An introduction to its occurrence and causes

Abstract

A number of neurotoxins have been found in herbal medicines and it is likely that others with more subtle or complex effects remain to be discovered. Severe poisoning by herbal products may be due to factors such as misidentification, adulteration, and poor processing of the plant material, and CNS “herbal” toxicity in particular may also be the result of the illicit use of recreational drugs. Any risk assessment must be considered in the context that herbal medicines are very variable both in quality and the way they are used, and also bearing in mind that a whole herb extract may produce test results quantitatively and qualitatively different than those of a constituent tested in isolation. The problems involved in assessing herbal neurotoxicity are similar to those in other areas of neurotoxicology, but are even more complex given the role of the CNS in controlling other systems of the body, and the fact that many neurotoxicity tests are not yet validated. Testing for developmental neurotoxicity is now recognized to be of crucial importance, but requires developing adapted methodologies. Increasing attention is being devoted to the development of in vitro systems for screening, but validation studies remain to be done to correlate in vitro results with neurotoxicological responses in whole animals.