The secret of the smell of frankincense

The difficulty was to find analytical methods that were precise enough to characterize these odorous substances present in very small quantities (a few hundred ppm) in the perfume, and therefore all the more difficult to detect..

To do this, the researchers used three kilograms of Somali frankincense essential oil from which they isolated a purified sample of about 1 mg of two odorants by a series of distillations, extractions and chromatographies. It was necessary to use a group of researchers trained to recognize the typical smell of incense, since only the human nose is sensitive enough to detect these constituents in small quantities in a mixture. It was then necessary to determine the molecular structure of these substances by nuclear magnetic resonance (NMR, the equivalent of MRI applied to molecules). The two molecules, which give the incense its peculiar “old church” smell, have been identified as (+) - trans- and (+) - cis-2-octylcyclopropane-1-carboxylic acids. This is the first time that these compounds have been discovered in nature. Then, in order to irrefutably validate their characterization established thanks to spectral analysis, the team synthesized each of these two compounds called "olibanic acids" (olibanum, another name for frankincense) by the researchers.

The latter have thus proved by synthesis that they are identical to the natural constituents. Thanks to this discovery, perfumers now have the possibility of manufacturing these molecules artificially, at will and of using them in different perfumes.