Essential oils & Chemotype

What is the chemotype of an essential oil?

Chemotype, also known as "chemotype" or "chemical race", refers to the "chemical signature" of an essential oil, i.e. a chemical sub-category within the same plant species. This concept first appeared in 1975 thanks to Pierre Franchomme. The European Union made it official in 2006 with the adoption of the REACH regulation, aimed at securing the manufacture and use of chemical substances in European industry.

The importance of essential oil chemotypes

The chemotype plays a key role in differentiating essential oils derived from the same plant species, as their biochemical composition can vary according to various factors: geographical origin, climate, soil type, sunlight, season, etc. These variations lead to different medicinal properties. These variations result in distinct medicinal and pharmacological properties. Knowing the chemotype is therefore essential to avoid errors in use that could have health consequences.

To determine these chemotypes, we use chromatography, a chemical separation method that measures variations in the concentration of components in a sample.

Examples of different chemotypes

• Rosemary (Rosmarinus officinalis)

  • Rosemary cineole: Rosemary grown in Tunisia or Morocco, rich in 1,8-cineole, produces an essential oil with expectorant properties, ideal for respiratory ailments.

  • Rosemary verbenone: Rosemary grown in Corsica contains more bornyl acetate, a substance beneficial to the liver and bile ducts.

  • Rosemary camphor: In Provence or southern Spain, rosemary is richer in camphor, which promotes cardiac and muscular activity, although it can be hepatotoxic.

• Thyme (Thymus vulgaris)

  • Thyme vulgaris: Thyme has 7 chemotypes: thymol, alpha-terpineol, carvacrol, geraniol, linalool, paracymene and thuyanol. For example, thyme grown near the Mediterranean gives off a strong, phenolized scent (carvacrol thyme), while thyme from Haute Provence has softer notes reminiscent of fine lavender (linalool thyme) or rose geranium (geraniol thyme). In other regions, you'll find fragrances of marjoram, eucalyptus or lemon verbena.

These examples illustrate the importance of knowing the chemotype for optimal use of essential oils.