Terpenes in Essential Oils

Terpenes are the most abundant and diverse class of compounds in essential oils. Built from the basic isoprene unit (C5H8), they are responsible for much of the aroma and therapeutic activity of essential oils.

The Isoprene Rule

All terpenes are constructed from isoprene units, classified by how many they contain:

Monoterpenes (C10) — The Most Volatile

Two isoprene units. Small, highly volatile, fresh-smelling.

• Limonene (citrus oils) — Uplifting, antimicrobial
• Alpha-pinene (pine, rosemary) — Anti-inflammatory, bronchodilator, memory-enhancing
• Myrcene (lemongrass) — Analgesic, sedative

Sesquiterpenes (C15) — Anti-Inflammatory Powerhouses

Three isoprene units. Heavier, less volatile, deeper aromas.

• Beta-caryophyllene (black pepper, copaiba) — CB2 agonist, anti-inflammatory
• Chamazulene (chamomile, blue tansy) — Potent anti-inflammatory
• Alpha-santalol (sandalwood) — Calming, skin-regenerating

Diterpenes (C20) — Rare in Essential Oils

Four isoprene units. Too large and heavy to be volatile — mostly found in resins and absolutes.

Oxidation Warning

Terpene hydrocarbons oxidize when exposed to air, light, and heat. The oxidation products can be skin irritants and sensitizers. This is why proper storage is essential.