ASCORBIC-ACID MAY PROTECT AGAINST HUMAN GASTRIC-CANCER BY SCAVENGING MUCOSAL OXYGEN RADICALS

High dietary ascorbic acid intake appears to protect against gastric c ancer, This may be due to its action as a scavenger of reactive radica l species formed in the gastric mucosa, resulting in a reduced level o f radical-mediated DNA damage, We have studied 82 patients, of whom 37 had Helicobacter pylori-associated gastritis, a condition which predi sposes to gastric cancer, Using electron paramagnetic resonance (EPR) spectroscopy we have demonstrated, for the first time, that ascorbyl r adicals are generated in human gastric mucosa, presumably as a result of scavenging of free radicals by ascorbic acid, Quantification of asc orbyl radicals demonstrates that there is a higher concentration in th ose patients with H.pylori gastritis compared with subjects with norma l histology (P < 0.01), We also found gastric mucosal luminol-enhanced chemiluminescence and malondialdehyde concentrations (which are belie ved to be markers of radical generation and tissue damage) to be highe r in patients with H.pylori gastritis compared with those with normal histology (P < 0.001 and P < 0.01 respectively), The observed concentr ations of the ascorbyl radical correlate with the level of luminol-enh anced chemiluminescence (r = 0.41, P < 0.001), but not with malondiald ehyde concentrations (r = 0.08, P = 0.47), Mucosal ascorbic acid and t otal vitamin C concentrations did not vary between histological groups , nor did they correlate with mucosal levels of the ascorbyl radical, chemiluminescence or malondialdehyde. These data suggest that ascorbic acid is acting as a scavenger of free radicals generated in human gas tric mucosa, The experiments therefore provide direct supportive evide nce for the hypothesis that ascorbic acid protects against gastric can cer by scavenging reactive radical species which would otherwise react with DNA, with resultant genetic damage.