Preparation of fatty acid cholesterol ester hydroperoxides was undertaken with the purpose of evaluating their biological effects on cell growth. Cholesterol stearate, oleate, linoleate and α-linolenate were oxidized using methylene blue as a photosensitizer. The structures of all compounds were established by mass spectrometry and by nuclear magnetic resonance. The photosensitized oxidation of cholesterol oleate gave two hydroperoxide isomers: 9- ...