Abstract
The main aim of investigations was to identify chemotypes and determine differences between some domestic hop varieties and wild hops, which were collected from some regions of Lithuania and cultivated at the same edafoclimatic conditions in hops collection of Kaunas Botanical Garden of Vytautas Magnus University. One of objectives was to compare essential oils of hops (2 years harvest) by the evaluation of volatiles content. Among the main components of hop essential oils monoterpenes (β-myrcene) and sesquiterpenes (α-humulene and β-caryophyllene) were determined using gas chromatography coupled with mass spectrometry (GC-MS). Retention parameters (t R, calculated retention index, and Kovats retention index) and m/z value of molecular ion for selected compounds from hop essential oils were determined. Samples were prepared by applying solid phase microextraction (SPME), supercritical fluid extraction (SFE) and accelerated solvent extraction (ASE). The steam distillation was used to obtain hop essential oils. The chemometric comparison of domestic and wild hops based on GC-MS analysis data was carried out. The obtained statistical results allow us to classify the investigated wild forms and domestic varieties of hops according to the similarities of their chemotypes. The concentration of β-myrcene, α-humulene in hop essential oils obtained from cones 2 years harvests is much higher than other volatile organic compounds (15.2–23.7 % in total contribution). In analysed essential oils β-farnesene is a constituent in higher quantity of hop essential oils obtained from cones from second time harvest than from cones from first harvest. This can be explained by the year-to-year vegetation conditions difference.
Highlights
It is commonly known, that hop cones were used in brewery for centuries, because of their aroma and provided bitterness (Zanoli and Zavatti 2008)
In 1926, a collection of hops was created at the Kaunas Botanical Garden of Vytautas Magnus University by K
Over 170–200 compounds can be separated and their quantities estimated using capillary GC analysis of hops essential oils in one run, which is a very suitable tool performing comparative study of different plants by so called chromatographic profiling or fingerprinting (Stankevičius et al 2007). Evaluation of those results by chemometric methods reveals the information analogous to that obtained in genetic analysis, but provides phytochemical composition data, which are indispensible for standardization and quality control of plant raw materials required in food or pharmaceutical industry
Summary
That hop cones were used in brewery for centuries, because of their aroma and provided bitterness (Zanoli and Zavatti 2008). Over 170–200 compounds can be separated and their quantities estimated using capillary GC analysis of hops essential oils in one run, which is a very suitable tool performing comparative study of different plants by so called chromatographic profiling or fingerprinting (Stankevičius et al 2007). Evaluation of those results by chemometric methods reveals the information analogous to that obtained in genetic analysis, but provides phytochemical composition data, which are indispensible for standardization and quality control of plant raw materials required in food or pharmaceutical industry. High resolution and ability to provide precise and accurate qualitative and quantitative data distinguishes GC-MS analysis as valuable tool for taxonomic studies of plants
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