The archeological and historical record shows that people across Asia,
Europe, and Africa used alkaloidal drugs as early as 2000 BCE. Alkaloids are
heterocyclic rings consisting of at least one nitrogen atom. They are the waste products
of plant metabolites and serve a wide variety of biological activities to human beings.
Nicotine, cytosine, atropine, scopolamine, cocaine, catuabine, quinine, quinidine,
dihydroquinine, papaverine, ephedrine, reserpine, ergotamine, caffeine, etc. are the
most important marketed plant alkaloidal drugs and their metabolites are described in
this chapter. Metabolism plays a central role in regulating the toxicity of a variety of
phytochemicals. Hepatic microsomal enzymes such as monooxygenase and putative
NADPH-FMN-reductase, carboxyl esterase, CYP2B6, CYP3A4, and CYP2D6 are
mostly involved in the metabolism of alkaloids. This chapter will be important for
future researchers.
Keywords: Cytochrome P650, Heterocyclic Ring, Hepatic Microsomal Enzymes, Marketed Alkaloids, Major Metabolites , Metabolic Pathway, Pharmacological Activities, Secondary Metabolites.
