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Although a wide range of terpene structures exist, few of them are biologically significant; by contrast, diterpenoids possess a rich pharmacology and include important compounds such as retinol, phytol or taxadiene.
Terpenes are classified by the number of carbons: monoterpenes (C 10), sesquiterpenes (C 15), diterpenes (C 20), as examples. The terpene alpha-pinene is a major component of the common solvent, turpentine. The one terpene that has major applications is natural rubber (i.e., polyisoprene).
Terpenoids are modified terpenes, [7] wherein methyl groups have been moved or removed, or oxygen atoms added. Some authors use the term "terpene" more broadly, to include the terpenoids. Just like terpenes, the terpenoids can be classified according to the number of isoprene units that comprise the parent terpene:
Monoterpenes are a class of terpenes that consist of two isoprene units and have the molecular formula C 10 H 16. Monoterpenes may be linear (acyclic) or contain rings (monocyclic and bicyclic). Modified terpenes, such as those containing oxygen functionality or missing a methyl group, are called monoterpenoids. Monoterpenes and monoterpenoids ...
Sesquiterpenes are a class of terpenes that consist of three isoprene units and often have the molecular formula C 15 H 24. Like monoterpenes, sesquiterpenes may be cyclic or contain rings, including many combinations. Biochemical modifications such as oxidation or rearrangement produce the related sesquiterpenoids. [1]
Triterpenes are a class of terpenes composed of six isoprene units with the molecular formula C 30 H 48; they may also be thought of as consisting of three terpene units. Animals, plants and fungi all produce triterpenes, including squalene, the precursor to all steroids. [1] [2]
For example, ajmalicine is a selective antagonist of α 1-adrenergic receptors and therefore has antihypertensive action. [ 55 ] [ 56 ] Yohimbine is more selective to α 2 adrenoceptor; [ 56 ] by blocking presynaptic α 2 -adrenoceptors, it increases the release of norepinephrine thereby raising the blood pressure.
The vast heterogeneity of structures underlying this class of compounds makes generalizations difficult; they're a subclass of terpenoids, oxygenated derivatives of terpene hydrocarbons. Terpenes in turn are formally made up of five-carbon isoprene units (The alternate steroid base is a terpene missing a few carbon atoms). Derivatives are ...