The Effects of Black Raspberry Lozenges on 4-Hydroxy-1-(3-pyridyl)-1-butanone-Releasing DNA Adducts in Buccal Cells and Urinary Levels of N'-Nitrosonornicotine and its Glucuronide in Active Smokers.

The tobacco constituent, N'-nitrosonornicotine (NNN) is a potential etiological agent in the development of oral cancer. NNN is metabolically activated to form DNA adducts that release 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) which was detected at higher levels in the oral cavity of smokers than non-smokers. Black raspberry (BRB) has been proposed as a preventive agent of oral cancer. In a phase 0 clinical trial, 40 active smokers (16 males, 24 females) consumed 5g of BRB lozenges daily for eight weeks. Each participant served as his/her own control. Buccal cells and urine were collected at baseline, during BRB administration, and washout period. In all smokers, BRB reduced, but not significantly, the levels of HPB-releasing DNA adducts (Baseline: 0.97 ± 0.51 and End-BRB: 0.61 ± 0.23 HPB/106 Guanine). A sex-specific response to BRB was observed: BRB had no effects in men, but in 16 of 24 women BRB significantly reduced the levels of HPB. We further tested the hypothesis that detoxification of NNN via N-glucuronidation by BRB may, in part, account for the inhibition of HPB levels. The ratio of NNN-N-Gluc to free NNN significantly increased (p = 0.028) from 1.29 ± 0.40 (baseline) to 2.77 ± 0.76 (End-BRB) in all 40 women as well as in female responders from 1.24 ± 0.60 (baseline) to 2.87 ± 1.00, but not in non-responders. The metabolic changes of NNN observed in our clinical trial indicate that BRB is a promising candidate for cancer interception and prevention of oral cancer in some, but not in all active smokers.