Bioavailability and antioxidant capacity of plant extracts rich in polyphenols, given as a single acute dose, in sheep made highly susceptible to lipoperoxidation

Plant extracts rich in polyphenols (PERP) could represent interesting alternative antioxidants but their use in ruminants needs further investigation since the antioxidant capacity of PERP could be altered by digestive processes. The aim of the study was to investigate the bioavailability and the antioxidant capacity of four PERP (rosemary; grape; citrus; marigold) in ruminants made highly susceptible to lipoperoxidation by a continuous linseed oil infusion (4% DM) in the duodenum. The PERP were given, as a single acute dose (10% DM), directly into the rumen of sheep (n 5) and blood was then collected every 3 h over a period of 30 h. Grape was particularly efficient to enhance the plasma total antioxidant status (P<0.05). Moreover, many new polyphenols were detected in the plasma and the identification of epicatechin in the grape group suggested that, contrary to monogastrics, ruminants can benefit from the antioxidant effect of polymeric proanthocyanidins. Finally, the four PERP tested, and more especially marigold, significantly reduced plasma susceptibility to liperoxidation (mean increase of lag phase: +5.9 min, P<0.02; mean reduction of oxidation rate: -1.7 A(234)/min, P<0.01). In conclusion, the digestive processes in ruminants do not inhibit the antioxidant properties of PERP in vivo and are beneficial by improving the biological effect of polymeric proanthocyanidins. Further experiments are now necessary to determine the optimum dose of administration and to characterize the bioactive molecules.