The Effects of Black Raspberry as a Whole Food–Based Approach on Biomarkers of Oxidative Stress in Buccal Cells and Urine of Smokers

Abstract

Cigarette smoke is a rich source of free radicals that can promote oxidative stress and carcinogenesis including head and neck squamous cell carcinoma (HNSCC) development; importantly, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-iso-prostaglandin F2α (8-isoprostane) are biomarkers of oxidative stress. Several mechanisms including the antioxidant properties of black raspberry (BRB) account for their chemopreventive effects. In the present clinical trial, we tested the hypothesis that BRB administration reduces biomarkers levels of oxidative stress in buccal cells and urine of smokers. One week after enrolling 21 smokers, baseline buccal cells and urine samples were collected before the administration of BRB lozenges for 8 weeks (5/day, 1 gm BRB/lozenge). Buccal cells and urine samples were collected at the middle and the end of BRB administration. The last samples were collected after the BRB cessation (washout period). We analyzed levels of 8-oxodG and 8-isoprostane (LC-MS/MS), urinary cotinine (ELISA) and creatinine (spectrophotometry). BRB significantly reduced the levels of 8-oxodG by 17.08% (p = 0.00079) in buccal cells and 12.44% (p = 0.034) in urine at the middle of BRB administration as compared to baseline; the corresponding values at the end of BRB administration were 16.46% (p = 0.026) in buccal cells and 25.72% (p = 0.202) in urine. BRB had no significant effect on the levels of urinary 8-isoprostane. BRB’s capacity to inhibit 8-oxodG formation of smokers’ buccal cells and urine is clearly evident and the reduction in 8-oxodG suggests antioxidant abilities are central to BRB’s HNSCC chemopreventive properties.