The name "terpene" is derived from the word "turpentine“. Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and flowers.
Most of the terpenoids are colorless, fragrant liquids which are lighter than water and volatile with steam. A few of them are solids e.g. camphor. All are soluble in organic solvent and usually insoluble in water. Most of them are optically active.
Terpenoids are universally present in small amount in living organism where they a numerous role in plant physiology as well as important function in all cellular membrane. They are the main constituent of essential oils of plants and flower.
Most natural terpenoids hydrocarbon have the general formula (C5H8)n. They can be classified on the basis of value of n or number of carbon atoms present in the structure. Classification of terpenoids (and example)
*Hemiterpenes - Prenol, isovalericacid
*Monoterpenes - geraniol, limonene, terpineol
*Sesquiterpenes - humulene, farnesenes, farnesol
*Diterpenes - cafestol, kahweol, cembrene, taxadiene, retinol, retinal, phytol
*Sesterterpenes - Geranylfarnesol
*Triterpenes - Squalene
*Tetraterpenes - lycopene,alpha-,beta-and gamma-carotenes
*Polyterpenes
The simpler mono and sesqui terpenes are chief constituent of the essential oils obtained from sap and tissues of certain plants and trees.
Monoterpenoids are a major class of compounds in essential oils. Monoterpenoid in plants: attracting pollinator (e.g. insect) to flowers, protection from herbivores and microbial infection
And monoterpenoids in insect: defence and pheromonal secretion.
Terpenoids - organic chemicals derived from the 5-carbon compound isoprene
