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Essential oil of Cannabis sativa L. strains

Vito Mediavilla and Simon Steinemann

        Mediavilla, Vito and Simon Steinemann 1997. Essential oil of Cannabis sativa L. strains. Journal of the International Hemp Association 4(2): 80 – 82. The aroma of hemp (Cannabis sativa L.) could be of considerable commercial value if evaluation of varieties and development of extraction methods led to a pleasing scent in the resulting essential oils. We compared the composition and smell of some fiber hemp and drug Cannabis essential oils isolated by steam distillation. The essential oil of some hemp strains contained particular monoterpenes and sesquiterpenes that imparted to the specimen a desireable scent. 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 Δ⁹-tetrahydrocannabinol (THC) concentration in the essential oils was very low and varied between 0.02% and 0.08%. The ratio of this compound to cannabidiol showed only small changes during steam distillation.

Introduction
        The Cannabis smell is a peculiarity of this plant. Its aroma does not originate from the terpenophenolic cannabinoids, but from the more volatile monoterpenes and sesquiterpenes (Lehmann 1995). Hashish detection dogs, for example, do not smell Δ⁹-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 an essential oil.
     Many utilizations for hemp essential oil are known. They impart the typical Cannabis aroma to such products as cosmetics, soaps, shampoos, creams, oils, perfumes and also to foodstuffs. Additional possible uses are for aroma therapy and as a means for plant protection. According to McPartland (1997), two essential hemp oil components (limonene and alpha-pinene) have a repellent effect against many insects. The bacteriostatic activity of hemp essential oil has been reported by Fournier et al. (1978). Although first trials of hemp essential oil used against potato late blight (Phytophthora infestans) were not promising (Krebs 1996), cannabinoid antifungal activity cannot be discounted.
     The aim of the work presented here was to assess the variability of hemp essential oil from different Cannabis strains.

Materials and methods
        Fiber and drug cultivars (Tab. 1) were grown in 1996 near Zurich, Switzerland (approximately 47º 25’ N, 8º 30’ E, 400 m elevation). The crop was harvested 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 still with 0.5 kg plant material took 30 minutes. The essential oil was collected using a lighter-than-water volatile oil apparatus consisting of a glass funnel. Monoterpene and sesquiterpene analyses were carried out by GC/MS, and cannabinoid analyses by GC alone.
Scent tests were performed with 15 volunteers who took part in smelling hemp essential oils diluted with jojoba oil (1: 5).

Results
        The yield of hemp essential oil amounted to approximately 1.3 liter/ton fresh weight, which corresponds to about 10 liters per hectare. No quantitative yield assessment was done.
     We could characterize 16 terpenoid compounds in the essential oil of different Cannabis strains (Tab. 2). The concentration of monoterpenes was generally higher than that of sesquiterpenes, varying from 47.9% to 92.1% of total terpene content. Sesquiterpene concentrations varied from 5.2% to 48.6%. The most abundant substance was myrcene, followed by trans-caryophyllene, alpha-pinene, trans-ocimene and alpha-terpinolene. The composition of the different essential oils varied greatly. For example, the oil of strain B 3985 TE was rich in alpha-pinene, beta-pinene and limonene concentration, ‘Felina 34’ was high in alpha-terpinolene and the fiber cultivar ‘Ferimon 12’ had a large caryophyllene oxide concentration. Drug types were generally lower in caryophyllene oxide content. The best fragrance rating (“quite good”) was ‘Felina 34’, and the one with the least favorable rating (“quite bad”) was ‘Fedora 19’ (Tab. 2).
     THC concentration in the essential oil was very low, even in drug varieties, reaching 0.08% in Swissmix (Tab. 3). THC concentration was lower and the ratio of THC to cannabidiol was not higher in the essential oil compared to the inflorescences.

Discussion
        The characterized compounds are the major constituents of hemp essential oil as described by Hendriks et al. (1975), Turner et al. (1980) and Ross and ElSohly (1996). Because of its low volatility and water insolubility (Malingré et al. 1975), THC concentrations in the essential oils were low. Therefore, the use of this steam distilled oil for drug purposes is not expected.
     Smell is, of course, a very subjective phenomenon. For that reason, smell test ratings varied considerably. Oils with high sesquiterpene concentrations received a low rating, meaning that they smelled badly. In contrast, oils with high monoterpene percentages (but a low alpha-humulene or caryophyllene oxide concentration) got a high rating. Surprisingly, a mixed oil from different strains received the best rating. This could be an important consideration for future commercial use.
     These preliminary results must be interpreted with caution. Harvest stage and the weather “just-before-harvest” may influence the quality of this essential oil, which could be developed into a promising product for the cosmetic, food, medical and plant protection sectors.