The genus Achillea consists of about 140 perennial herbs native to the Northern hemisphere. Traditional indications of their use include digestive problems, liver and gall-bladder conditions, menstrual irregularities, cramps, fever, wound healing. The Commission E approves its internal use for loss of appetite and dyspeptic ailments (gastric catarrh, spastic discomfort), externally it is used in form of sitz bath or as a compress against skin inflammation, slow healing wounds, bacterial or fungal infections. In the last decades, pharmacological studies became intensive, although human clinical investigations are still rare. Recent findings have confirmed several traditional uses. The largest number of data accumulated for antioxidant and anti-inflammatory effects. There are positive results on the analgesic, anti-ulcer, choleretic, hepatoprotective and wound healing activities. First results on other interesting therapeutical areas - antihypertensive, antidiabetic, antitumor, antispermatogenic activities -need confirmation. Yarrow can be used also as an insect repellent. Contact dermatitis as adverse effect may be connected to sesquiterpenes. The diversity and complexity of the effective compounds of yarrow species explains the broad spectrum of their activity. According to the literature the pharmacological effects are mainly due to the essential oil, proazulenes and other sesquiterpene lactones, dicaffeoylquinic acids and flavonoids. Synergistic actions of these and other compounds are also supposed. Achillea species have different chemical and therapeutical values. Despite of numerous data, correct evaluation of the results is difficult because of missing generally accepted taxonomical nomenclature. The used chemical-analytical methods and bio-assays are utmost diverse, making the comparison complicated. Further research on the activity is needed using exactly defined plant material, standardized methods and chemical analysis.
Based on the present knowledge of essential oil composition of species belonging to the genus Achillea the factors, which may influence the composition with regard to plant biology, production and application are discussed.According to studies from the last 15 years, a mean of 54 compounds have been identified in samples of different species. Among them, the largest number of components (149 compounds) were found in the oils of A. millefolium, A. pannonica and A. collina. The monoterpenes, 1,8-cineole, camphor, borneol, α-and β-pinenes are among the five most abundant components. Beside chamazulene, the most frequently identified sesquiterpenes are β-caryophyllene and its oxide. The presence of chamazulene seems to remain a characteristic, but it is not ubiquitous to the members of the Millefolium group. The heritance mechanism of sesquiterpenes, especially chamazulene, seems to be established, while we know relatively less about the genetic regulation of the monoterpene compounds. During ontogenesis, major differences could be found between the stages before and after flower development. The phenological phase assuring the highest level of azulenes seems to be during flowering. Composition and compositional changes of an essential oil within the Achillea genus in different plant organs seems to depend on the species. In several cases a dominance of sesquiterpene components above the monoterpenes was found in the vegetative organs. The most important difference seems to be the lack or low amount of chamazulene as artefact in the extracts compared to the distillates.
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