β-ionone shown to be a key intermediate in the synthesis of vitamin A. Can be isolated from the volatile oil of Boronia megastigma Nees, Rutaceae or by condensing citral with acetone. From animal experiments it can be concluded that β¬-ionone is absorbed after oral exposure. Metabolism takes place mainly in the liver. ¬ β-Ionone has only low acute toxicity after oral ingestion. The substance naturally occurs as a biogenic volatile organic compound and shows a ubiquitous occurrence in the air due to emissions from plants or surface waters.