What is a chemotype essential oil?

What is a chemotype essential oil or HECT in Aromatherapy?

After a gradual evolution of research, modern aromatherapy reached its maturity in 1980, when biochemists isolated the active ingredients from molecules. Doctor Pierre Franchomme, with the concept of chemotype, helped to improve the identification of the active ingredients in the extracts used. From that point on, science redoubled its investigations into plant science.

What is a chemotype?

The chemotype of an essential oil (H.E) is in fact defined by the level of the molecule most present in an essential oil. It is essential to know the concept of “chemotype” also called chemotype. Of defined biochemical race, as soon as we approach aromatherapy. This precision given to the essential oil ultimately makes it possible to define the molecule or molecules that are biochemically active on a certain number of clinically studied pathologies.

One example among many others, however, will allow us to illustrate this fundamental notion provided by Pierre Franchomme:

THYME is a plant widely used for the therapeutic properties of its essential oil. Of course, there are multiple biotopes where this plant species develops easily.

  •  1st chemotype:

Thymol thyme : Thymus vulgaris CT thymol (this H.E contains about 40% thymol, which defines its chemotype)

  • 2nd chemotype:

Thyme thujanol: Thymus vulgaris CT thujanol (it contains about 50% thujanol, which defines its chemotype)

  • 3rd chemotype:

Thyme linalool: Thymus vulgaris CT linalool (it contains about 60% linalool, which defines its chemotype)

A molecule is generally only taken into account in an H.E if it exceeds 10%.

Recognized internationally and widely used in scientific and academic publications, the precision of the chemotype of an essential oil, associated with the Latin scientific name, therefore allows the perfect understanding of the mode of action of essential oils which will lead to the use of a therapeutic, aromatherapy, natural, powerful and effective. This identification allows, above all, to know the level of quality of an essential oil. If, on the packaging of this one, this information does not appear, it is very likely that the quality of this essential oil is mediocre.

The demonstration of the chemotype:

The chemotype used in aromatherapy makes it possible to identify within the same species chemical variations of secondary metabolites which are due in particular to environmental factors (altitude, sunshine, temperature, humidity, etc.). Thus, the gasoline produced by two plants of the same species, despite their very similar genotype and morphology, may exhibit large variations in chemical composition. It is therefore a very important concept in aromatherapy.

An aromatic plant will therefore provide totally different essential oils depending on where they are harvested or where they come from. Biochemically different, two chemotypes will present not only different therapeutic activities but also very variable toxicities.

You can extract an essence from any organ as soon as it has the structures to produce it. Thus many EOs come from flowers, leaves, seeds, fruits, rhizomes, etc. The same plant from the same biotope will be able to synthesize essences with very different compositions and odors depending on the producing organ in question.

The best-known example is that of the bitter orange tree from which we can extract 3 distinct H.E. The leaves will give the EO of petit grain bigarade, the flowers will give the EO of neroli, while the peel of the fruit will give the essence of bitter orange peel.

What does the term HECT mean?

It is essential to use quality essential oils, 100% pure and natural, of controlled origin and chemotype, not terpeneless, with the name HEBBD (which means that the Essential Oil is Botanically and Biochemically Defined). Other laboratories use the HECT label, similar to that of HEBBD, which stands for Chemotyped Essential Oil and which is also a guarantee of the quality of essential oils from a botanical and biochemical point of view.

The lack of knowledge of this capital concept and the lack of precision leave the door open to therapeutic failures, but above all, to the toxicity of certain essential oils. Thus, faced with the therapeutic power of HECTs, a study based not only on knowledge but also on experience allows an optimal use for a natural medicine of shock for the third millennium.

Some laboratories surrounded by expertise have understood this well. They deploy costly and sophisticated analysis methods to ensure consistent, repeatable, and flawless quality. All the laboratories specializing in aromatherapy, which distribute essential oils in pharmacies, are obliged by the French authorities to provide a certificate of analysis for each batch marketed.

All the essential oils distributed in the pharmacy network, ie in pharmacies, are analyzed and chemotyped by an independent laboratory, which then issues a certificate of analysis. The latter must in fact be able to be consulted on request, for optimal transparency between the distributor (pharmacist) and the customer (patient).

The main biochemical families of essential oils in Aromatherapy:

  • MONOTERPENIC ALCOHOLS (Monoterpenols):

(Linalool, menthol, citronellol, geraniol, thujanol-4, terpineol, borneol, terpinene-4-ol, nerol, etc.)

  • SESQUITERPENIC ALCOHOLS (Sesquiterpenols):

(Carotol, viridiflorol, farnesol, cedrol, bisabolol, patchoulol, santalol, eudesmol, globulol, nerolidol, sclareol, etc.)


(1,8 cineole, ascaridole, linalooloxide, piperitonoxide, bisabololoxide, menthofuran, ascaridiol, etc.)


(α-pinene, limonene, gamma-terpinene, delta-3-carene, β-pinene, camphene, α-terpinene, paracymene, etc.)


(Humulene, chamazulene, zingiberene, azulene, longifolene, cedrene, himachalene, caryophyllene, curcumene, germacrene, α-farnesene, etc.)


(Thymol, carvacrol, eugenol, guaiacol, etc.)


(Cinnamaldehyde, benzaldehyde, cuminaldehyde, etc.)


(Citronellal, geranial, neral, etc.)


(Bornyl acetate, geranyl acetate, linalyl acetate, menthyl acetate, neryl acetate, methyl salicylate, benzyl acetate, eugenyl acetate, terpenyl acetate, myrenyl acetate, phloryl acetate, isobutyl angelate , petasyl angelate, citronellyl tiglate, linalyl isovalerate, bornyl isovalerate, benzyl benzoate, methyl methylanthranilate, methyl cinnamate, methyl methroxyanthranilate, etc.)

  • ETHERS (Phenols methyl ethers):

(Trans and cis-anethole, methyl-chavicol, methyl-eugenol, diethylstilbestrol, β-arasone, etc.)


(Carvone, menthone, verbenone, camphor, thujone, tagetone, piperitone, pulegone, D and L carvone, acetone, methyl-n-nonyl ketone, italidione, artemisia ketone, cryptone, frenchone, borneone, pinocamphone, pinocarvone, germacroma, α and β-atlantone, davanone, germacrone, α and β-vetivone, aryl-tumorone, diosphenone, etc.)


(Alantolactone, artemisinin, massoia lactone, parthenolide, etc.)


(Angelicine, umbelliferone, herniarine, imperatorine, scopoletol, psoralen, bergaptene, 1,2 benzopyrene, visnadine, limettine, umbelliprenine, etc.)


(3-n-butylphthalide, ligustilide, sedanolide, etc.)

Arnaud C. (Doctor of Pharmacy)

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