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.

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The impact of browsing on vegetation depends on the relative density and species composition of browsers. Herbivore density and plant damage can be either site-specific or change seasonally and spatially. For juniper (Juniperus communis) forests of a sand dune region in Hungary, it has been assumed that plant damage investigated at different temporal and spatial scales would reflect selective herbivory. The level of juniper damage was tested for a possible correlation with the concentration of plant secondary metabolites (PSMs) in plants and seasonal changes in browsing pressure. Heavily browsed and nonbrowsed junipers were also assumed to differ in their chemical composition, and the spatial distribution of browsing damage within each forest was analyzed to reveal the main browser. Long-term differences in local browsing pressure were also expected and would be reflected in site-specific age distributions of distant juniper populations. The concentrations of PSMs (essential oils) varied significantly among junipers and seasons. Heavily browsed shrubs contained the lowest oil yield; essential oils were highest in shrubs bearing no damage, indicating that PSMs might contribute to reduce browsing in undamaged shrubs. There was a seasonal fluctuation in the yield of essential oil that was lower in the summer period than in other seasons. Gas chromatography (GC) revealed differences in some essential oil components, suggesting that certain chemicals could have contributed to reduced consumption. The consequential long-term changes were reflected in differences in age distribution between distant juniper forests. These results confirm that both the concentration of PSMs and specific compounds of the essential oil may play a role in selective browsing damage by local herbivores.

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