Bixin or 6,6'-diapo-phi,phi'-carotenodioic acid (mono)-methyl ester, isolated and purified as the major and water insoluble carotenoid from "urucum" (Bixa orellana, L.) seeds, was submitted to complexation with a natural cyclodextrin model (alpha-CD) using both column percolation and sonication. This water-soluble product was analyzed by spectrophotometry and H-1 NMR to confirm complex formation as well as protection for the carotenoid from the effects of light and air or the combination of both. Also evaluated was the capability for free or complexed bixin as quencher/scavenger of free radicals such as alpha-alpha-diphenyl-beta-picrylhydrazide (DPPH) and its degradation time course when challenged with ozone generated directly in the pigment solution or indirectly in the surrounding environment. The results showed that the complexed form of bixin is more resistant than free bixin to the damage caused by light and air or their combination besides and shows improved water solubility as required for novel formulations of medical or pharmaceutical interest. (C) 2004 Elsevier Ltd. All rights reserved.