Essential oils are complex mixtures of volatile compounds obtained from aromatic plants. Many factors affect the chemistry of essential oil extracted from the same species including climate, elevation, soil composition, conditions of growth, time and way of gathering plants and method of extraction. They play an important role in aromatherapy, pharmacy, cosmetics, food and perfume industries. Their effect on body and mind has been known for centuries, but the mechanism of action is not completely researched. In this Master's thesis, we analysed the composition of volatile compounds in thirty essential oils and four supercritical extracts from selected Asteraceae species using gas chromatography coupled with mass spectrometry (GC-MS). We compared samples from the same plant species obtained from different geographical origin and plant parts. We researched scientific databases to gather information about activities of essential oils and supercritical extracts and the most common compounds. By studying data from in vitro and in vivo studies we tried to find connections between activites of essential oils or supercritical extracts and activities of the most common compounds. The GC-MS analysis of composition showed that some essential oils and supercritical extracts can contain up to hundred different compounds. Usually there are two or three main compounds which are present in a content larger than 10 %. Essential oils from plant species of the same genus mostly had similar compounds but in different contents, while composition and contents of supercritical extracts varied more. We also noticed differences in composition based on the geographical origin and plant parts. All studied essential oils showed antimicrobial activities. The most diverse activities have been shown for Anthemis nobilis essential oil having antimicrobial, anti-inflammatory, analgesic, antidepressant, anxiolytic and sedative activities, and Artemisia annua essential oil with antimicrobial, antioxidant, analgesic, sedative and anticonvulsant activities. Some activites of essential oils and supercritical extracts are also supported by the activities of their compounds. But we can not assume that essential oils will have the same activities as the particular compounds because the synergy between compounds plays an important role.
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