Terpenoids, also referred to as terpenes, are the largest group of natural compounds. Many terpenes have biological activities
and are used for the treatment of human diseases. The worldwide sales of terpene-based pharmaceuticals in 2002 were approximately
US $12 billion. Among these pharmaceuticals, the anticancer drug Taxol® and the antimalarial drug Artimesinin are two of the
most renowned terpene-based drugs. All terpenoids are synthesized from two five-carbon building blocks. Based on the number
of the building blocks, terpenoids are commonly classified as monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), and sesterterpenes (C25). These terpenoids display a wide range of biological activities against cancer, malaria, inflammation, and a variety of
infectious diseases (viral and bacterial). In last two decades, natural-product bioprospecting from the marine environment
has resulted in hundreds of terpenoids with novel structures and interesting bioactivities, with more to be discovered in
the future. The problem of supply is a serious obstacle to the development of most terpenoid compounds with interesting pharmaceutical
properties. Although total chemical synthesis plays a less important role in the production of some terpenoid drugs, it has
contributed significantly to the development of terpenoid compounds and terpene-based drugs by providing critical information
on structure-activity relationships (SAR) and chiral centers as well as generating analog libraries. Semisynthesis, on the
other hand, has played a major role in the development and production of terpenoid-derived drugs. Metabolic engineering as
an integrated bioengineering approach has made considerable progress to produce some terpenoids in plants and fermentable
hosts. Cell culture and aquaculture will provide a solution for the supply issue of some valuable terpenes from terrestrial
and marine environments, respectively. Recent advances in environmental genomics and other “-omics” technologies will facilitate
isolation and discovery of new terpenoids from natural environments. There is no doubt that more terpenoid-based clinical
drugs will become available and will play a more significant role in human disease treatment in the near future.