The key difference between terpenes and terpenoids is that terpenes are simple hydrocarbons whereas terpenoids are modified terpenes containing different functional groups and oxidized methyl groups.

Terpenes and terpenoids are organic compounds. Terpenoids are derived from terpenes. Various different plants and animals produce terpenes, e.g. conifers and some insects. Terpenoids are also naturally occurring compounds.

CONTENTS

1. Overview and Key Difference
2. What are Terpenes 
3. What are Terpenoids 
4. Side by Side Comparison – Terpenes vs Terpenoids in Tabular Form
5. Summary

What are Terpenes?

Terpenes are a large group of organic compounds which are simple hydrocarbons. These compounds are produced by various plant and animal species, including coniferous plants and some insect species. Often, terpenes have a strong odour and it can protect the plants by deterring herbivores and by attracting predators and parasites of herbivores.

Figure 01: Limonene is a Common Terpene

The term terpene derives from “turpentine” in which terpene is the major component. Terpenes can be found as a major biosynthetic building block in biological systems. For example, steroids are a derivative of terpenes.

We can observe terpenes and terpenoids as the major components in the essential oils of various types of plants and flowers. These essential oils are widely used as fragrances in perfume production and traditional medicine production.

Terpenes form from the units of isopentenyl pyrophosphate via biosynthetic routes. There are two metabolic pathways for the formation of a terpenoid form a terpene; Mevalonic acid pathway and MEP/DOXP pathway. Some common terpenes include Limonene, carvone, humulene, and taxadiene. We can classify terpenes into different groups as hemiterpenes, monoterpenes, sesquiterpenes, and diterpenes.

When considering the properties and uses of terpenes, these compounds have desirable properties to be used in the food industry, cosmetic industry, pharmaceutical industry, and biotechnology. In addition, terpenes are important active ingredients in natural agricultural pesticides. The trees that contain terpenes release high amounts of terpene in warm weather conditions.

What are Terpenoids?

Terpenoids or isoprenoids are a large group of organic compounds that are derived from isoprene. These are naturally occurring organic compounds that originate from the 55-carbon compound, isoprene and terpenes (isoprene polymers). These are multicyclic structures having oxygen-containing functional groups. Most of the known natural products are terpenoids. Sometimes the terms terpene and terpenoid are used interchangeably but these are different from each other because terpenes are simple hydrocarbon compounds while terpenoids are complex compounds having different functional groups.

Figure 02: A Simple Terpenoid Structure

Plant terpenoids have aromatic qualities which are important in traditional herbal remedies. These compounds contribute to the scent of eucalyptus, cause the flavour of cinnamon, cloves, and ginger. Also, these terpenoid compounds cause the yellow colour in sunflowers and the red colour in tomatoes. There are different known terpenoids including citral, menthol, camphor, cannabinoids, etc.

There are different classes of terpenoids such as hemiterpenoids, monoterpenoids, diterpenoids, sesquiterpenoids, etc. Terpenoids are modified terpene molecules (modified by adding or removing oxygen atoms).

What is the Difference Between Terpenes and Terpenoids?

Terpenes and terpenoids are organic compounds. The key difference between terpenes and terpenoids is that terpenes are simple hydrocarbons whereas terpenoids are modified terpenes containing different functional groups and oxidized methyl groups. Hemiterpene, monoterpene, diterpene, sesquiterpene, etc. are terpenes while hemiterpenoid, monoterpenoid, diterpenoid, sesquiterpenoid, etc. are types of terpenoids.

Below tabulation summarizes the differences between terpenes and terpenoids.

Summary – Terpenes vs Terpenoids

Terpenes and terpenoids are organic compounds. The key difference between terpenes and terpenoids is that terpenes are simple hydrocarbons whereas terpenoids are modified terpenes containing different functional groups and oxidized methyl groups.

Reference:

1. “What Are Terpenes?” Medical News Today, MediLexicon International, Available here.

Image Courtesy:

1. “Limonene-2D-skeletal” By Original file:Limonene-2D-skeletal.png by User:Benjah-bmm27derivative work: user:Karlhahn – Limonene-2D-skeletal.png (Public Domain) via Commons Wikimedia

2. “Terpineol alpha” By Calvero. – Own work (Public Domain) via Commons Wikimedia

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