Essential oil of some hemp genotypes

Vito Mediavilla and Simon Steinemann
Swiss Federal Research Station for Agroecology and Agriculture, Reckenholzstrasse 191, 8046 Zurich, Switzerland, Email: vito.mediavilla@fal.admin.ch, http://www.admin.ch/sar/fal/

erschienen in: (1997) Journal of the Internatinal Hemp Association 4(2): 80-82

Abstract

The aroma of hemp (Cannabis sativa L.) could be of considerable commercial value if varieties and extraction methods led to a pleasing scent of the extracted essential oils. We compared the composition and the smell of the essential oil of some fibre and drug hemp genotypes after steam distillation. The essential oil of some hemp genotypes contained particular monoterpenes, sesquiterpenes and had a special smell. These preliminary one-year results do not take into account the influence that harvest time and the weather just-before-harvest could have on the quality of the essential oil. The D ⁹-tetrahydrocannabinol (THC) concentration in essential oil was very low and varied between 0.02% and 0.08%. THC-CBD ratio showed only small changes during steam distillation.

Introduction

The Cannabis smell is a peculiarity of this plant. Most of its aroma does not originate from the cannabinoids (terpenophenolics) but from more volatile compounds which belong to the monoterpenes and sesquiterpenes (Lehmann 1995). Hashish narcotic dogs for example do not smell D ⁹-tetrahydrocannabinol (THC) but are able to smell the sesquiterpene caryophyllene oxide (Stahl and Kunde 1973). According to Turner et al. (1980) 58 monoterpenes and 38 sesquiterpenes have been identified in hemp. Using steam distillation it is possible to concentrate most of these components to essential oil.

Many utilisations for essential hemp oil are known. They allow to impart the typical Cannabis aroma to products like cosmetics, soaps, shampoos, creams, oils, perfumes and also to food stuff. Additional uses are for medication (aroma therapy) and as a mean for plant protection. Bacteriostatic activity of essential hemp oil has been reported by Fournier et al. (1978). Although first trials where essential hemp oil was used against potato late blight (Phytophthora infestans) were not promising (Krebs 1996) its antifungal activity can not be excluded. According to McPartland (1997) two essential hemp oil components (limonene and a -pinene) have a repellent effect against many insects.

The aim of the work presented here was to assess the genetic variability of essential hemp oil from different Cannabis genotypes.

Material and methods

Fibre and drug cultivars (Tab. 1) were grown in 1996 near Zurich, Switzerland (approximately 47^o 25’ N, 8^o 30’ E, 400 m elevation). Harvest was done between the end of flowering and seed ripeness. Flowers and the upper leaflets of female or hermaphrodite plants were cut by hand and freshly distilled. Steam distillation in a copper distillator with 0.5 kg plant material took 30 minutes. The essential oil was collected using a higher-than-water volatile oil apparatus. Monoterpene and sesquiterpene analyses were carried out by GC/MS, cannabinoid analyses by GC alone. have been executed with Fifteen volunteers took part in smelling tests where a solution of essential hemp oil: jojoba oil (1: 5) was used.

[Tab. 1]

Results

The yield of essential hemp oil amounted to approximately 1.3 litre/ton fresh weight, this corresponds to about 10 litres per hectare. No quantitative yield assessment was done.

We could characterize 17 compounds in the essential oil of different hemp genotypes (Tab. 2). The concentration of monoterpenes was generally higher than the one of sesquiterpenes varying from 47.9% to 92.1%. Sesquiterpenes concentration varied from 5.2% to 48.6%. The most abundant substance was myrcene, followed by trans-caryophyllene, a -pinene, trans-ocimene and a -terpinolene. The composition of the different essential oils varied much. For example the oil of the genotype B 3985 TE was high on a -pinene, b -pinene and limonene concentration, Félina 34 high a -terpinolene and the fibre cultivar Férimon 12 had a high caryophyllene oxide concentration. Drug genotypes were generally lower in caryophyllene oxide concentration. The genotype with the best fragrance rating was Félina 34 (quite good), and the one with the least favourable rating was Fédora 19 (quite bad) (Tab. 2).

[Tab. 2] (51 KB)

The THC concentration in the essential oil was very low, even in drug varieties, reaching 0.08% in Swissmix (Tab. 3). THC concentration and THC-CBD ratio was not higher in the essential oil than in the inflorescences.

[Tab. 3]

Discussion

The characterized compounds are the major constituents of components described in essential hemp oil by Hendriks et al. (1975), Turner et al. (1980) and Ross and ElSohly (1996). To our knowledge, phthalic acid diethyl ester has not been characterized in hemp before. This component is common and its origin could be an impurity. Because of its water insolubility (Malingré et al. 1975) the THC concentration in the essential hemp oil was low. Therefore, no abuse of hemp essential oil for drug purposes by water steam distillation has to be expected.

Smell is of course a very individual phenomenon. For that reason smell test ratings have varied considerable. Oils with high sesquiterpenes concentration, probably because of polymerisation reactions, received low rating, meaning that they smelled badly, in contrast oils with low a -humulene or caryophyllene oxide concentration got high rating. Surprisingly, a mix oil of different genotypes received the best rating. This could be important for future commercial use.

These preliminary results of the essential oil composition of some hemp genotypes have to be interpreted with caution. Harvest stage and the weather just-before-harvest may influence the essential oil quality. Essential hemp oil could be a promising product for cosmetic, food, medical and plant sector.

Acknowledgements

We thank I. Slacanin (Laboratoire Central, Bienne) for the analyses of monoterpenes and sesquiterpenes and R. Brenneisen (Institute of Pharmacy, University of Bern) for the analyses of cannabinoids.

References

Fournier G., M. R. Paris., M. C. Fourniat and A. M. Quero, 1978. Activité bactériostatique d’huiles essentielles de Cannabis sativa L.. [Bacteriostatic activity of Cannabis sativa L. essential oil.] Annales pharmaceutiques françaises 36 (11-12): 603-606.

Hendriks H., T. M. Malingré, S. Battermann and R. Bos, 1975. Mono- and sesqui-terpene hydrocarbons of the essential oil of Cannabis sativa. Phytochemistry 14: 814-815.

Krebs H., 1996. Personal communication, Swiss Federal Research Station for Agroecology and Agriculture.

Lehmann T., 1995. Chemische Profilierung von Cannabis sativa L. [Chemical profile of Cannabis sativa L.] Doctoral Thesis, Pharmazeutisches Institut Universität Bern.

Malingré T., H. Herndriks, S. Battermann, R. Bos and J. Visser, 1975. The essential oil of Cannabis sativa. Planta medica 28: 56-61.

McPartland J. M., 1997. Personal communication.

Ross S. A and M. ElSohly, 1996. The volatile oil composition of fresh and air-dried buds of Cannabis sativa. Journal of Natural Products 59: 49-51.

Stahl E. and R. Kunde, 1973. Die Leitsubstanzen der Haschisch-Suchhunde. [Leading substances for hashish narcotic dogs.] Kriminalistik 9: 385-388.

Turner C. E., M. A. Elsohly and E. G. Boeren, 1980. Constituents of Cannabis sativa L. XVII. A review of the natural constituents. Journal of Natural Products 43 (2): 169-234.

 

Table 1. Hemp genotypes and harvest stage.

* = variety mixture

[Tab. 2] Chemical composition of essential oils of some Cannabis sativa L. genotypes (51 KB)

Table 3. Cannabinoid concentration in female or hermaphrodite inflorescences and in the essential oil of two hemp genotypes

THC = D ⁹-tetrahydrocannabinol
CBD = cannabidiol

* not distilled dry material

** from fresh steam distilled inflorescences