The biological activities of extracts from skin and edible part of red onion have been investigated. Crude extracts of red onion were obtained separately with acetone, ethanol and aqueous solution of solvents. Extracts from onion edible part showed somewhat lower activity. Furthermore, high activity of skin extracts against bacteria Escherichia coli, Pseudomonas fluorescens and Bacillus cereus and against fungi Aspergillus niger, Trichoderma viride and Penicillium cyclopium was observed.
The aim was to obtain extracts with high anthocyanin content, which show stability during storage and would be interesting for commercial applications as natural colorants. Single-step batch extractions were performed with ethanol, ethyl-acetate and acetone in different ratios with water as well as two-step extractions, combining SFE and conventional batch extractions. The most efficient conventional solvents in single-step extractions were mixtures of organic solvent and water at 60 °C. Pre-treatment of natural material with supercritical CO2 improved the extraction of polyphenols.