The extent of oxidative DNA damage is considered a biomarker of carcinogenic process and could be investigated in population studies using easily obtained cells. The oxidized DNA base adduct 8-hydroxy-2-deoxyguanosine (8-OHdG) released by enzymatic hydrolysis of DNA is commonly assayed by high performance liquid chromatography with electrochemical detection. It is expressed as a ratio of 8-OHdG to unoxidized deoxyguanosine. We modified and improved this method, determined the optimal time for harvesting buccal mucosa cells (BMC), assessed whether they mirror peripheral circulating blood cell DNA damage, and compared the anticoagulants, heparin, and EDTA for consistency in measurement of leukocyte 8-OHdG. Thirty-one healthy participants, randomized into two groups, donated BMC and blood samples. Samples were collected at baseline and either 3 or 7 days after baseline. Results showed no correlation between 8-OHdG/deoxyguanosine ratios in BMC and peripheral blood leukocytes at any time point regardless of harvest time. BMC had much higher oxidative DNA damage, but displayed a 25.6% reduction in the oxidized DNA adduct level (P < 0.04) at 3 days after baseline. Leukocytes collected in heparin and EDTA had similar 8OHdG/deoxyguanosine ratios; however, EDTA was preferred, as it produced a clean nuclear pellet without hemoglobin contamination, and the results were less variable. This improved assay shows within subject stability over time in both leukocyte and BMC DNA damage, increasing the probability that small intervention differences can be detected in healthy subjects. Buccal cells provide an accessible pool of epithelial cells that represents higher levels of DNA damage than circulating leukocytes. (Cancer Epidemiol Biomarkers Prev 2008;17(1):212 -9)

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The objective of the present study was to compare fresh (F) use and the effects of boiling (B) and deep-fat frying (DF) on the leaf of Citrus hystrix on total phenolic content, the types and amounts of flavonoids and their total antioxidant capacities (TAC), as measured by three different assays: oxygen radical absorption capacity, ferric reducing/antioxidant power, and scavenging effect on the 2,2-diphenyl-1-picrylhydrazyl free radical. Boiling decreased TAC values on the three assays. The amount of total flavonoids calculated as aglycone equivalents of eight identified flavonoids (cyanidin, myricetin, peonidin, quercetin, luteolin, hesperetin, apigenin and isorhamnetin) determined by high-performance liquid chromatography was 1,129 (DF), 1,104 (F) and 549 (B) mg/100 g freeze-dried weight (dry matter exclude fat). Hesperetin was the predominant flavonoid. The total phenolic content expressed as grams of gallic acid equivalents/100 grams fresh weight (excluding fat) was 2.0, 1.9 and 1.8 in F, DF and B samples, respectively. These results suggest that method of processing can significantly affect the content of flavonoids and their TAC values.