Part 4: Terpene Hydrocarbons—Monoterpenes


The most widely represented class of hydrocarbons in essential oils is the terpenes. The basic unit of every variety of terpene is a five-carbon molecule called an isoprene; however, isoprenes do not occur in nature as free molecules. Instead, multiple isoprene units are joined together by chemical bonding to form molecules composed of 10, 15, 20, etc. carbons. This class of molecule can be identified from its scientific name, which typically uses the suffix -ene.

When a chemical bond forms between two isoprene units, a 10-carbon molecule called a monoterpene results. Monoterpenes can assume many shapes including cyclic, straight, and branched varieties. Common physical characteristics of monoterpenes are a low molecular weight (meaning they are small and light compared to other types of molecules), clear in color, free flowing (not viscous), high volatility, and strong aroma. You will see below that monoterpenes are present in varying amounts in nearly every essential oil! Common monoterpenes found in essential oils are limonene, pinene, terpinene, and cymene.

  • Cleansing1
  • Antioxidant2*
  • Protective to cells and promotes normal cell growth3*
  • Repels insects4
  • Stimulating and enhancing effects on mood and cognitive health5

Essential Oil Main Monoterpene Constituent (s) Amount
Grapefruit5 limonene Approximately 97%
Wild Orange1,5 limonene Approximately 95%
Lemon1,5 limonene,  pinene Approximately 95%
Lime1,5 limonene, terpinene Approximately 85%
Frankincense3*,5 pinene, limonene Approximately 75%
White Fir5 limonene, pinene Approximately 75%
Juniper Berry1,5 pinene, sabinene, myrcene Approximately 75%
Cypress5 pinene, carene Approximately 70%
Bergamot1,5 limonene, terpinene Approximately 50%
Black Pepper2*,5 limonene, carene Approximately 50%
Coriander5 pinene, terpinene Approximately 45%
Dill1,5 limonene, phellandrene Approximately 40%
Rosemary4,5 pinene, camphene Approximately 35%
Melaleuca1 terpinene Approximately 35%
Marjoram5 terpinene Approximately 30%
Fennel5 limonene Approximately 25%


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