Terpenoids

Terpenoids, also known as isoprenoids, are a large and diverse class of naturally occurring organic chemicals derived from five-carbon isoprene units assembled and modified in thousands of ways. They are found in all classes of living things and are the largest group of natural products.

Structure and Biosynthesis

Terpenoids are derived biosynthetically from units of isoprene, which has the molecular formula C5H8. The basic molecular formulas of terpenoids are multiples of that, (C5H8)n where n is the number of linked isoprene units. This is called the isoprene rule or the C5 rule. The isoprene units may be linked together "head to tail" to form linear chains or they may be arranged to form rings. One can consider the isoprene unit as one of nature's common building blocks.

Terpenoids are modified by enzymes to create the complex structures of the molecules. The modifications include oxidation or rearrangement of the carbon skeleton, often resulting in a change in the functional groups. The ability of these enzymes to create such a vast array of chemical structures from a single starting material is a remarkable example of biochemical diversity.

Classification

Terpenoids can be classified by the number of isoprene units in the molecule. A prefix in the name indicates the number of terpene units needed to assemble the molecule.

• Monoterpenes (2 isoprene units)
• Sesquiterpenes (3 isoprene units)
• Diterpenes (4 isoprene units)
• Sesterterpenes (5 isoprene units)
• Triterpenes (6 isoprene units)
• Tetraterpenes (8 isoprene units)
• Polyterpenes (large number of isoprene units)

Functions

Terpenoids contribute to the scent of eucalyptus, the flavors of cinnamon, cloves, and ginger, the yellow color in sunflowers, and the red color in tomatoes. Several terpenoids have been used for medicinal purposes. They have roles in traditional herbal remedies and are under investigation for antibacterial, antineoplastic, and other pharmaceutical functions.

See Also

• Isoprene
• Enzymes
• Biochemical
• Eucalyptus
• Cinnamon
• Cloves
• Ginger
• Sunflowers
• Tomatoes

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