March 17, 2016

Natural vs Synthetic: Clarifying the Terms

Alexis St-Gelais, M. Sc., chimiste - Popularization

Laboratoire PhytoChemia is a business, and as any other business, we do use concepts that are commonly understood the same way by all our employees. Such is the case for the "natural" and "synthetic" designations for molecules we encounter in our analyzes. Taking a critical step back, these might create unintentional confusion within our growing readership, here or on other social media. I thus feel that giving more details about our understanding of these definitions might be of use for anyone interested in the results we provide.

At PhytoChemia, we commonly define "natural" and "synthetic" compounds as follows:

A natural compound is a molecule that has been obtained directly from a natural source, or occurs unintentionnally as the result of the spontaneous decomposition or transformation of a native molecule during extraction. The second part of the definition is required to properly describe specific cases. For example, chamazulene as a molecule does not occur in Matricaria recutita. However, during the process of heating to extract essential oils, matricin (another molecule that occurs as part of the normal metabolism of Matricaria recutita) thermally rearranges to chamazulene, and formation of the latter is more or less inherent to the processing of essential oil from the plant. For example, linalool is synthethized (made) by the plant the following way:
Figure 1: Pathway A - Linalool biosynthetic pathway

The synthetic designation, on the other hand, is used to describe any compound that has been transformed by an abiotic (i. e., occurring outside a living organism) phenomenon on a voluntary basis, independantly of its method of extraction. It does not automatically implies that the said molecule has been processed from petroleum derivatives (although this is perfectly possible).

For example, linalool can be produced by multiple method in lab. One of these method use camphene (which is usually produced by pinenes, isolated from essential oils or turpentine):
Figure 2: Pathway B - Linalool synthesis from camphene

Another method use compounds produced strictly from petroleum products:
Figure 3: Pathway C- Linalool synthetis from petroleum derivative
You can find more information on linalool synthesis in this excellent document too (the link will download a .doc file that can be opened with Microsoft Word or any other text processor).

The above is what we understand to be natural and synthetic at PhytoChemia. But the internal logic of these terms must be kept in mind. One could perfectly buy linalool and linalyl acetate isolated from natural sources, blend them with an orange essential oil, and forge a bergamot essential oil. By all means, the resulting product would be perfectly natural - even if adulterated! So, as far as our reports are concerned, the absence of "synthetic" material does not correspond to unadulterated.

Other definitions of synthetic vs. natural could be employed, however. For example, within scientific literature, "natural" mostly refers to the fact that a molecule of a given structure can occur in nature, regardless of how it was obtained in the first place. Accordingly, "synthetic" is then used for compounds that have no known natural source. Following this logic, linalool obtained by chemical transformation of pinene (pathway B) or from petroleum (pathway C) is still a natural compound, because linalool occurs in nature. Thus, with this definition, it is possible to fully synthetize natural molecules. This really is a more scholarly understanding of things, and is more useful to categorize molecules known to mankind than to establish adulterations.

"Synthetic" is also often reported to describe compounds strictly obtained from petroleum derivatives, like linalool from pathway C. Similarly, benzoic acid can be produced from toluene, itself refined from petroleum or coal. It can also be isolated from the natural benzoin resin, and many other plants. Both of these "varieties" of benzoic acid will have exactly the same properties, but the first could be called synthetic according to the petro-centered definition. The latter is somewhat too restrictive to be of use in our reports.

Hopefully, the text above clarifies what we have on our mind when using these terms at PhytoChemia. No one is perfect, so in case of doubt, it always is better to ask the analyst what was implied when a specific term is employed.

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