ABSTRACT
In the last few years, a large branch of knowledge known as “phytomedicine” has developed; it deals with the therapeutic benefits that have been obtained from the use of plant-derived substances. Many phytomedicines are known to exert diverse biological activities against human diseases. Phytomedicines contain numerous secondary metabolite compounds; major ones include the terpenoids, flavonoids, alkaloids, steroids and saponins. Many of these are concentrated into hydrophobic liquids such as essential oils that can be effectively used in treating human diseases and as supportive health care agents. They have a low toxicity to normal tissues, are highly well tolerated and are, therefore, relatively safe. Current research shows that herbal constituents containing terpenoids exert both therapeutic activities and toxicity effects. However, clinical trials with these components, especially the terpenoids, have yielded conflicting results. In comparison with the extensive knowledge of terpenoids chemistry, little is known about the bioactivity of their respective constituents such as hemiterpenoids, monoterpenoids, diterpenoids, carotenoids, sesquiterpenoids, polyprenols, phytosterols, brassinosteroids, and triterpenoids. The mode of action—considering they have either synergistic or antagonistic interactions in the presence of other chemicals—sometimes interferes negatively with their beneficial properties. Therefore, a better approach may be to use single enantiomeric terpenoids or well-defined terpenoid compositions in the treatment of human disease. This chapter discusses the toxicity and pathophysiology of terpenoids in human health.
