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 carot enoids in lung cancer, we investigated the extent of beta -carotene degrada tion by gaseous phase of cigarette smoke, and the kinetics of its degradati on in vitro at 20 degreesC. We also determined the preliminary spectral cha racteristics of smoke-degraded beta -carotene. On average, 78% of beta -car otene solution in hexane (7.0 muM) was degraded by 12 puffs of smoke (equiv alent to two cigarettes) over an exposure period of four hours. Degradation followed first-order kinetics with a 40.7% decrease in beta -carotene conc entration for each log unit of cigarette smoke exposure (r(2) = 0.986). The degradation products absorb maximally at much lower wavelengths compared t o intact beta -carotene, and give a diffused absorbance band between 320-41 0 nm. Further work is needed to determine the extent of carotenoids degrada tion by cigarette smoke in vivo, to identify the degradation products and t o elucidate the role of such products in lung carcinogenesis. (C) 2001 Else vier Science Inc. All rights reserved.