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 5 g of BRB lozenges daily for 8 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-glucuronide 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.