What are Terpenes?

“Terpenes, any member of a group of hydrocarbons that are often found in plants and animals and are believed to have evolved from isoprene, a hydrocarbon with five carbon atoms bonded to eight hydrogen atoms (C5H8).”

The name is frequently used to refer to the terpenoids, which are these hydrocarbons’ oxygenated derivatives. Terpenes are a wide category of volatile unsaturated hydrocarbons present in plant essential oils, particularly in conifers and citrus trees. They are based on the formula C5H8, which is a cyclic molecule.

Terpenes are aromatic chemicals present in many plants, but they are most usually associated with cannabis due to the large amounts found in cannabis plants. Many plants, including cannabis, pine, and lavender, as well as fresh orange peel, have aromatic chemicals that give them their distinct perfume.

Table of Contents

Classification of Terpenoids

Terpenoids, also known as isoprenoids, are a wide and diversified group of naturally occurring organic compounds formed from isoprene, a 5-carbon molecule, and terpenes, which are isoprene polymers.

Most natural terpenes hydrocarbons have the general formula (C5H8)n. They can be classified on the basis of the value of n or the number of carbon atoms present in the structure.

Each class can be further subdivided into subclasses according to the number of rings present in the structure.

  1. Acyclic Terpenoids: They contain an open structure.
  2. Monocyclic Terpenoids: They contain one ring in the structure
  3. Bicyclic Terpenoids: They contain two rings in the structure.
  4. Tricyclic Terpenoids: They contain three rings in the structure.
  5. Tetracyclic Terpenoids: They contain four rings in the structure.

General Properties of Terpenoids

  • Most of the terpenoids are colourless, 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.
  • They are open-chain or cyclic unsaturated compounds having one or more double bonds. Consequently, they undergo an addition reaction with hydrogen, halogen, acids, etc. A number of additional products have antiseptic properties.
  • They undergo polymerization and dehydrogenation.
  • They are easily oxidised nearly by all the oxidising agents. On thermal decomposition, most of the terpenoids yield isoprene as one of the products.

General Methods of Structure Elucidation of Terpenes

  • UV Spectroscopy: In terpenes containing conjugated dienes or alpha, beta-unsaturated ketones, UV spectroscopy is a very useful tool. The values of lambda(max) for various types of terpenoids have been calculated by applying Woodward’s empirical rules.

There is generally good agreement between calculation and observed values. Isolated double bonds, alpha, beta-unsaturated esters, acids, and lactones also have characteristic maxima.

  •  IR Spectroscopy: IR spectroscopy is useful in detecting groups such as a hydroxyl group (-3400cm-1) or an oxo group (saturated 1750-700cm-1). Isopropyl group, cis and trans also have characteristic absorption peaks in the IR region.
  • NMR Spectroscopy: This technique is useful to detect and identify double bonds, determine the nature of the end group and also the number of rings present, and also to reveal the orientation of the methyl group in the relative position of double bonds.
  • Mass Spectroscopy: It is now being widely used as a means of elucidating the structure of terpenoids. It is used for determining molecular weight, molecular formula, nature of functional groups present and relative positions of double bonds.

Importance of Terpenes

Terpenes have a vital influence on a cannabis strain’s scent and flavour. They may also generate psychedelic effects in combination with cannabinoids and other cannabis plant components. It’s difficult to reach any firm conclusions regarding this because study on more than 400 terpenes in the plant is still in its early stages.

The main component of essential oils extracted from the sap and tissues of specific plants and trees is the simple mono- and sesquiterpenes. Diterpenoids and triterpenoids are not steam volatile. They are produced from plants and trees of the gums and resins. Carotenoids are a category of chemicals that includes tetraterpenoids.

Frequently Asked Questions on Terpenes


What are terpenes used for?

Terpenes are highly fragrant chemicals that give plants and herbs like rosemary and lavender, as well as some animals, their distinct scents. Isolated terpenes are used to generate the flavours and fragrances of a variety of common items, including perfumes, body products, and even foods.


Do terpenes have medical benefits?

Terpenes have anti-inflammatory, antioxidant, analgesic, anticonvulsive, depressive, anxiolytic, anticancer, antitumor, neuroprotective, anti-mutagenic, anti-allergic, antibiotic, and anti-diabetic activities, according to various in vitro, animal, and clinical trials.


Can terpenes be harmful?

Inhaling pure, concentrated terpenes can cause damage and irritation to the lungs and may cause further damage once absorbed into the bloodstream. Some terpenes are directly toxic as well such as benzene or methacrolein.


What are terpenes good for?

Terpenes are natural compounds that are found in plants and insects. With a wide variety of therapeutic effects, terpenes can help the body destroy bacteria, detoxify, relax and more.


What is the difference between terpenes and essential oils?

It might sound like essential oils and terpene extracts are the same thing. They are indeed similar, but there are some key differences. The main difference is that essential oils contain all the volatile components in a given plant species, while terpenes are isolated and removed from everything else.


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