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

Objective: To determine the potential antioxidant effect of rutin (quercetin-3-O-beta-rutinoside) supplementation. Design: A 6-week randomized single-blind placebo controlled trial was conducted; 500 mg rutin supplement was compared to an equivalent amount of glucose placebo. In addition, a pharmacokinetic study was carried out. Setting: The Rowett Research Institute, Aberdeen, UK. Subjects: Eighteen healthy non-obese normocholesterolaemic female volunteers in the age range 18-48 y. Main outcome measures: Plasma flavonoids, ascorbic acid, tocopherols and caratenoids, plasma antioxidant capacity, lymphocyte DNA damage, blood chemistry and haematology, liver function tests, urinary malondialdehyde, 8-hydroxy-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 function. Plasma flavonoids were significantly elevated in the rutin-supplemented group. Endogenous oxidation of pyrimidines was significantly decreased in both rutin- and placebo-treated volunteers. There was no significant change in the level of urinary 8-hydroxy-2'-deoxyguanosine or urinary malondialdehyde in either group. A linear correlation was observed between urinary malondialdehyde and urinary 8-iso-prostaglandin F-2 alpha (R = 0.54, P < 0.01). Conclusion: Six weeks' rutin supplementation significantly elevated the levels 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 the placeba- and rutin-supplemented subjects may reflect seasonal changes in other dietary antioxidants.