Humans are exposed to foreign compounds such as drugs, household products and environmental chemicals by swallowing or breathing. Also, food is considered a foreign compound. Such foreign compounds can be non-essential and non-functional to life, and commonly are referred to as xenobiotics. Some xenobiotics are not toxic; however, many of them are potentially toxic or become toxic after conversion to metabolic intermediates. A considerable number of foreign compounds belong to non-polar, lipophilic substances. Lipophilic compounds are not soluble in water. Metabolic conversion of...