Toxic essential oils: anxiolytic, antinociceptive and antimicrobial properties of the yarrow Achillea umbellata Sibth. et Sm. (Asteraceae) volatiles.

Many plant species are used for medicinal purposes without the knowledge of their possible toxic effect. The ethnopharmacologically renowned genus Achillea L. (Asteraceae) is even more troublesome in this respect since different taxa are believed to have the same beneficial properties as A. millefolium. According to the median lethal i.p. dose (LD(50)=853 mg/kg, mice), the volatiles of Achillea umbellata Sibth. et Sm. are more toxic than the thujone-containing essential oils (LD(50)>960 mg/kg). A GC-MS analysis of A. umbellata oil revealed the presence of a series of fragranyl esters (six new natural products). The major constituents of this oil, the rare monoterpene alcohol fragranol and fragranyl acetate, and one more ester (benzoate), as well as the oil itself, showed antianxiety, analgesic and, in some instances, paralyzing properties at 50-150 mg/kg but these are very likely sign of intoxication and not of possible beneficial effects of the plant volatiles. Testing of antimicrobial activity demonstrated that the oil possesses moderate activity against pathogenic microorganisms, but the effect of the oil differs in pro- and eukaryotic cells. According to the results obtained, fragranol may be considered as the main active principle responsible for the observed activity/toxicity.

Misidentification of tansy, Tanacetum macrophyllum, as yarrow, Achillea grandifolia: a health risk or benefit?

Tansy, Tanacetum macrophyllum (Waldst. & Kit.) Sch. Bip., is often misidentified by herb collectors as yarrow, Achillea grandifolia Friv. With the former, cases of poisoning induced by its ingestion are well documented, but the latter is widely used for ethnopharmacological purposes. The aim of this study was to estimate, based on the volatile metabolite profiles of the two species, the potential health risk connected with their misidentification. GC and GC-MS analysis of the essential oils hydrodistilled using a Clevenger-type apparatus from A. grandifolia, T. macrophyllum, and two plant samples (reputedly of A. grandifolia, but in fact mixtures of A. grandifolia and T. macrophyllum) obtained from a local market, resulted in the identification of 215 different compounds. The main constituents of A. grandifolia oil were ascaridole (15.5%), alpha-thujone (7.5%), camphor (15.6%), borneol (5.2%) and (Z)-jasmone (6.4%), and of T. macrophyllum oil, 1,8-cineole (8.6%), camphor (6.4%), borneol (9.1%), isobornyl acetate (9.5%), copaborneol (4.2%) and gamma-eudesmol (6.2%). The compositions of the oils extracted from the samples obtained from the market were intermediate to those of A. grandifolia and T. macrophyllum. Significant differences in the corresponding volatile profiles and the literature data concerning the known activities of the pure constituents of the oils, suggested that the pharmacological action of the investigated species (or their unintentional mixtures) would be notably different. It seems, however, that misidentification of T. macrophyllum as A. grandifolia does not represent a health risk and that the absence of the toxic alpha-thujone from T. macrophyllum oil may in fact be regarded as a benefit.