The degradation of (all-E)-beta-carotene by cigarette smoke

The effects of cigarette smoke in promoting the degradation of (all-E)-beta-carotene have been studied, but some conflicting results promoted a further study. beta-Carotene was solubilized in hexane and challenged with filtered cigarette smoke both at room temperature and at -20 degrees C. The products arising from smoke-induced oxidation were assessed using a combination of HLPC-DAD, LC-MS and GC-MS. At room temperature the degradation of beta-carotene was very rapid, with only a few products being detected using HPLC-DAD. A range of volatile products including beta-ionone, beta-cyclocitral and 5,6-epoxy-beta-ionone were detected using GC-MS. In contrast, when the reaction was slowed (by reducing the reaction temperature), a much wider range of products could be detected by HPLC-DAD, including 4-nitro-beta-carotene and several of its geometric isomers. These degradation products suggest that the C4 position on the beta-carotene end-group plays a key role in initiating free radical attack.