Bioavailability and efficiency of rutin as an antioxidant: a human supplementation study

Objective: To determine the potential antioxidant effect of rutin (querceti n-3-O-beta-rutinoside) supplementation. Design: A 6-week randomized single-blind placebo controlled trial was condu cted; 500 mg rutin supplement was compared to an equivalent amount of gluco se placebo. In addition, a pharmacokinetic study was carried out. Setting: The Rowett Research Institute, Aberdeen, UK. Subjects: Eighteen healthy non-obese normocholesterolaemic female volunteer s in the age range 18-48 y. Main outcome measures: Plasma flavonoids, ascorbic acid, tocopherols and ca ratenoids, plasma antioxidant capacity, lymphocyte DNA damage, blood chemis try and haematology, liver function tests, urinary malondialdehyde, 8-hydro xy-2-deoxyguanosine and 8-iso-prostaglandin F-2 alpha. Results: Eighteen volunteers completed the trial. Rutin supplementation did not induce any adverse changes in blood chemistry or indices of liver func tion. Plasma flavonoids were significantly elevated in the rutin-supplement ed group. Endogenous oxidation of pyrimidines was significantly decreased i n both rutin- and placebo-treated volunteers. There was no significant chan ge in the level of urinary 8-hydroxy-2'-deoxyguanosine or urinary malondial dehyde in either group. A linear correlation was observed between urinary m alondialdehyde and urinary 8-iso-prostaglandin F-2 alpha (R = 0.54, P < 0.0 1). Conclusion: Six weeks' rutin supplementation significantly elevated the lev els of three plasma flavonoids (quercetin, kaempferol and isorhamnetin) but there was no significant change in plasma antioxidant status. The decrease in the level of endogenous base oxidation in lymphocyte DNA seen in bath t he placeba- and rutin-supplemented subjects may reflect seasonal changes in other dietary antioxidants.