Bioavailability and antioxidant effect of dietary phenolic compounds in lamb tissues

Abstract

Phenolic compounds are organic compounds distributed all over the plant kingdom and they are products of the secondary metabolism of plants. The main characteristic of phenolic compounds is to be antioxidant compounds. Phenolic compounds are present daily in human and animal diets. The study of bioavailability of phenolic compounds in monogastric has been widely studied but not in polygastric animals. The objective of the experiments carried out in the present thesis was to investigate whether different polyphenolic compounds or their metabolites could be detected in the tissues of lambs that had been fed previously with a specific diet. For the Experiment 1, lambs where fed with a diet supplemented with quebracho extract (characterised to be a rich source of profisetinidin compounds, a group of condensed tannins). In the other experiment (Experiment 2), lambs where fed on pasture, specifically with Lolium perenne (this plant belong to Poaceae family plant, which is not rich in polyphenolic compounds but contains some simple polyphenolic compounds). In both studies there was a control group, where lambs were fed with a commercial concentrate diet. In both experiments, no signals of the compounds present in feed samples or their corresponding metabolites were found in liver or plasma samples from lambs fed the respective diets. Furthermore, in both experiments the antioxidant status was measured in lamb tissue extracts that had either been treated or not treated with a Solid Phase Extraction (SPE) step. This step was used to purify samples and to isolate any phenolic compounds in the final extract. These experiments sought to investigate whether phenolic compounds have a direct or indirect antioxidant effect in lamb tissues. In both experiments it has been showed that phenolic compounds present in diets from Experiment 1 and Experiment 2 can improve the antioxidant capacity of tissues via an indirect effect. Further research is required to study the bioavailability of polyphenols compounds in ruminants and to understand the possible mechanism of action of polyphenolic compounds in improving the antioxidant status in ruminants.