Comparison of extraction methods for analysis of flavonoids in onions

Onions are known to contain high levels of flavonoids and a comparison of the efficiency, reproducibility and detection limits of various extraction methods has been made in order to develop fast and reliable analytical methods for analysis of flavonoids in onions. Conventional and classical methods are time- and solvent-consuming and the presence of light and oxygen during sample preparation facilitate degradation reactions. Thus, classical methods were compared with microwave (irradiation) extraction, ultrasonic liquid extraction and accelerated solvent extraction

Bioactive metabolites in crops, diets and human samples

The objective of the PhD-project is to characterize bioactive metabolites, such as polyphenols, in selected crops and investigate the influence of different organic farming systems on the ability of crops to synthesize bioactive compounds with health promoting effects. The study includes two organic and one conventional farming system and is part of the OrgTrace project (content, bioavailability and health effects of trace elements and bioactive components in organic agricultural systems), where harvest takes place in autumn 2007 and 2008

OrgTrace – No Difference in Levels of Bioactive Compounds found in Crops from Selected Organic and Conventional Cultivation Systems

The objective of the present study was to compare the content of selected bioactive compounds in organically and conventionally grown crops, and to evaluate if the ability of the crops to synthesize selected secondary metabolites was systematically affected by growth systems across different growth years as well as soil types. The results showed that contents of neither polyacetylenes and carotenoids in carrots, flavonoids in onions, nor phenolic acids in carrots and potatoes were significantly influenced by growth system. Thus it could not be concluded that the organically grown crops had higher contents of bioactive compounds than the conventionally grown. This indicates that giving preference to organic products because they contain more bioactive components is doubtfull. However, there are many other reasons for the consumer to choose organic food products, including: no pesticide residues in foods, animal welfare, and environmental protection