In line with a part of its strategic plan concerned with educating pharmacists about substances used in complementary medicine, the medicinal and aromatic plants section of the International Pharmaceutical Federation organised a symposium on volatile oils during the recent FIP congress in Vienna. Professor Peter Houghton (professor of pharmacognosy, department of pharmacy, King’s College London) reports
Until recently, the pharmaceutical use of volatile oils — sometimes called essential oils — has been mainly in the traditional areas of flavourings, perfumes, carminatives and rubefacients. However, the past few years have seen an enormous increase in their use in aromatherapy and associated commercial products. The symposium was organised because of concerns about the quality of oils used in such products and about the claims often made for them in advertising, promotional material and in articles in popular literature.
Why oils with the same name may vary in quality
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| Origanum vulgare: different genetic chemotypes of oregano produce different volatile oils |
Professor Jeno Bernath (Budapest, Hungary) highlighted the reasons for variation
in volatile oils that occurs in the plant kingdom. About 200 different oils
were common articles of commerce but their occurrence was restricted to particular
families of plants, so that the British Herbal Pharmacopoeia described 17 members
of the Lamiaceae family and 13 Asteraceae species.
Oils having very similar characteristics could be obtained from very different
plants and Professor Bernath cited the example of oils of the oregano type,
containing a high level of carvacrol, which were obtained commercially from
different species belonging to at least six families.
Conversely, the same species might produce different oils depending on its genetic
chemotype. For example, Oreganum vulgare subspecies viride had three strains
producing oils with high amounts of carvacrol, thymol and terpinen-4-ol, respectively.
The quality and quantity of oil could also vary according to the life cycle
of the plant and the environment in which it was grown. Further variations in
chemical composition could arise as a result of the production process, a classic
example being the production of chamazulene from matricin during the distillation
of chamomile oil. The recent introduction of extraction using supercritical
carbon dioxide was producing oils of different composition from those produced
by steam distillation.
Professor Bernath emphasised that, with so many possible causes of variability,
the name of the oil gave very little guarantee of its chemical composition and,
thereby, its biological effect, making the need for regulation and detailed
criteria for official oils imperative.