By Benoit Roger, Ph. D.
Always looking for a deeper knowledge of our surrounding plants, we recently distilled eastern teaberry or American wintergreen (Gaultheria procumbens) freshly harvested in our local boreal forest (Saguenay, QC, Canada).
Leafs of wintergreen and beginning of the distillation
The crushed leaves of eastern teaberry has an odor that is well known in Québec, the scent of pink ”paparmanes” which are now an integral part of the Québec culture. This menthol-type scent is due to the methyl salicylate accounting for about 98 % of the essential oil obtained from this plant.
We regularly receive wintergreen essential oils (G. procumbens ou G. fragrantissima) for analysis but they almost always come from Nepal and China. G. procumbens is also quite common in the forest of Canada and the north of United States but it is nowadays only used in some artisanal products such as herbal tea. We must admit that the Asian equivalent or the synthetic methyl salicylate is a cheaper alternative and even a much cheaper alternative in the latter case.
Then, the eastern teaberry is one of the lost treasures we have in our forests. Let’s rediscover and use it!
If the composition of wintergreen essential oil is very simple, its distillation is a bit more complex. First, the methyl salicylate is not free into the plant but bounded to a sugar. This non-volatile glucidic complex named gaultherin must be hydrolyzed prior distillation so that the methyl salicylate can be distilled. Also, wintergreen essential oil is one of the rare oils that are denser that water and it doesn’t decant easily. Then, the distillation of eastern teaberry requires a still with a special design (a separator for heavy oils and for better yields, the possibility to distill with cohobation) and a maceration in hot water prior distillation so that the plant enzymes can free the methyl salicylate.
For more technical details on our distillation test, 2.7 kg of plant (stems and leaves) have been harvested and macerated in water the night before distillation. Plant and water have been heated to about 50 °C and the still/extractor has been insulated for the night to activate and maintain the enzymatic activity. This maceration step has been performed as described by Guenther . It would be interesting to validate these parameters (temperature, time, crushing or not) to maximize the hydrolysis of gaultherin and then distillation yield. After 5 hours of distillation with cohobation (continuous re-injection of the hydrosol into the still), we obtained about 20 g of essential oil. This is a yield of about 0.75 % which is a bit higher than the value given by Guenther (0.6 %). As cited in litterature, the hydrosol stays very cloudy during distillation and clarifies when it’s finished.
When we collected the essential oil and during a subsequent olfactory evaluation, we did not notice an odor very different from those of commercial batches we use to analyse but surprisingly, when we opened the still lid, we got a strong coconut scent emanating from the distilled plant. This observation stayed outstanding until the analyses when we identified some uncommon compounds in the essential oil and the hydrosol. To double check these identifications, we harvest a bit more eastern teaberry and we distilled it using the same method in a small glass apparatus and we made new analyses (tables 1 et 2).
Table 1 : Composition of the essential oil of Gaultheria procumbens (Saguenay, QC, Canada)
Table 2 : Composition of the hydrosol of Gaultheria procumbens (Saguenay, QC, Canada)
No doubt, the essential oil from the Canadian Gaultheria procumbens (or at least those of Saguenay) contains some compounds we don’t find in the Asian Gautheria: the tuberolactone and the massoia lactone. These compounds are found in the osmanthus absolute (Osmanthus fragrans) or tuberose absolute (Polianthes tuberosa) and the essential oil of massoia bark (Cryptocarya sp.). These compounds have a fruity/coconut scent  and coconut/cream scent  respectively.
The occurrence of these compounds at relatively low concentration in the essential oil does not seem to have a great impact on its scent (it could be the case after a partial evaporation of methyl salicylate) but as we observed a strong coconut scent when we opened the still, it may be possible to work on a distillation or extraction method to obtain an essential oil, a fraction or an extract that is more concentrated in these uncommon compounds. If not and if its occurrence is verified in other places in Canada and United States, it would simply be a marker of origin. Anyway this is a nice demonstration that revisiting the plants around us can lead to the (re)discovery of lost treasures. Get you still and let’s distill!
 Guenther E., The essential oils vol. VI. 1952. Krieger editions, p 3-7.
 Bourdineaud J.P., Ehret C., Petrzilka M. Optically active lactones, World Patent WO/94107887, April 19, 1994.
 Mosciano G., P&F 19, No. 1 (27), 1994.