Beta-carotene degradation by cigarette smoke in hexane solution in vitro

Smokers have lower levels of serum carotenoids and have higher incidence of lung cancer. As a part of our interest in the role of smoke-degraded carotenoids in lung cancer, we investigated the extent of beta -carotene degradation by gaseous phase of cigarette smoke, and the kinetics of its degradation in vitro at 20 degreesC. We also determined the preliminary spectral characteristics of smoke-degraded beta -carotene. On average, 78% of beta -carotene solution in hexane (7.0 muM) was degraded by 12 puffs of smoke (equivalent to two cigarettes) over an exposure period of four hours. Degradation followed first-order kinetics with a 40.7% decrease in beta -carotene concentration for each log unit of cigarette smoke exposure (r(2) = 0.986). The degradation products absorb maximally at much lower wavelengths compared to intact beta -carotene, and give a diffused absorbance band between 320-410 nm. Further work is needed to determine the extent of carotenoids degradation by cigarette smoke in vivo, to identify the degradation products and to elucidate the role of such products in lung carcinogenesis. (C) 2001 Elsevier Science Inc. All rights reserved.