Comparative analysis of nicotine dynamics and antioxidant enzyme activity in high-tar and low-tar tobacco combustion users and healthy volunteers

This study investigated the influence of smoking exposure and reported cigarette type on antioxidant enzyme activity and nicotine and cotinine profiles in smokers. Participants were classified as low-tar (LT, n = 23) or high-tar (HT, n = 21) smokers based on self-reported cigarette type, and these reports were further confirmed using expired CO levels. A control group of non-smokers (n = 28) was also selected based on expired CO measurements for comparison. Plasma nicotine and cotinine concentrations were quantified using HPLC before and after incubation with ascorbic acid, whereas superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase-1 (GPx-1) activities were determined using ELISA. LT smokers exhibited significantly reduced CAT activity (p = 0.0021) and a modest, non-significant increase in the nicotine-to-cotinine (NC) ratio after incubation. In HT smokers, the post-incubation NC ratio correlated positively with oxidative stress markers, including the R ratio (r = 0.571, p = 0.007), SC ratio (r = 0.611, p = 0.004), and SOD activity (r = 0.592, p = 0.006). These findings suggest that differences in smoke exposure and reported cigarette type are associated with variations in redox-related measures under the experimental conditions studied. • High-tar smokers showed higher SOD activity and altered antioxidant balance. • Low-tar smokers showed a small, non-significant NC ratio change with ascorbic acid incubation. • Post-ascorbic acid NC ratio was associated with oxidative stress indices in high-tar smokers. • CAT activity was lower in low-tar smokers, with small changes in GPx-1 levels. • Nicotine–cotinine measures differed between low- and high-tar smokers after ascorbic acid incubation.