Probiotics and berry-associated polyphenols: catabolism and antioxidative effects

Abstract: Oxidative stress can cause damage to DNA, proteins and lipids and is associated with inflammation and various human diseases as cancer, atherosclerosis, and autoimmune diseases. Polyphenol-rich diet, such as fruits and berries, may act as antioxidants and prevent oxidative stress and, thereby, associated diseases. Administration of lactic acid bacteria (LAB) can affect the microflora in the gastrointestinal (GI) tract and may increase the capability of the bacterial flora to digest polyphenols. Some strains of Lactobacillus may break down phenolic acids and hydrolyzable tannins into phenolic metabolites that are more easily absorbed in the body and may enhance antioxidative effects. The aim of this thesis was to clarify the protective effects of polyphenol-rich fruits and berries alone or in combination with different strains of LAB on oxidative stress in mice. Furthermore, transformation of polyphenols in a bilberry beverage by LAB was examined. Supplementation with rosehips of the rose species Rosa pimpinellifolia or an LAB mixture decreased lipid peroxidation and oxidative stress in colon of mice after ischemia-reperfusion (I/R) injury. Adding an LAB supplement to the rosehips increased the concentrations of phenolic compounds, antioxidative capacity and total phenolic content in cecum. Rosehips of R. piminellifolia are a rich source of cyanidin-3-O-glucoside and this compound and its degradation product, protocatechuic acid, were detected in the cecum content. Administration of bilberry, either alone or together with Lactobacillus plantarum HEAL19, decreased lipid peroxidation and oxidative stress in colon of mice after I/R injury. A chokeberry-supplement showed no antioxidative effect. Bilberry was found to have a more complex anthocyanin profile than chokeberry. Higher concentrations and a more varied composition of anthocyanins were seen in colon than in cecum. More phenolic metabolites were found in the intestines of bilberry-fed mice than in the chokeberry-fed ones. Chokeberry or bilberry alone decreased the number of LAB on the colonic mucosa but addition of L. plantarum HEAL19 prevented this reduction. In a more extensive ischemia-reperfusion injury, diet supplemented with bilberry, but without addition of different LAB strains, reduced lipid peroxidation and protected the small intestine against oxidative stress. The highest concentration and recovery of anthocyanins was seen in the ileal content followed by that of colon and finally cecum. Anthocyanin arabinosides, and especially malvidin-3-O-arabinoside, were accumulated in the colon content. Glucosides and galactosides of malvidin, peonidin and petunidin seemed to be digested by the microflora in the cecum. Supplementation of bilberry to the diet influenced the composition of cecum microflora. Anthocyanins in bilberry beverages inoculated with different LAB strains, alone or in combination with wine yeast, decreased during 3 weeks incubation at 30 degrees Celsius. Arabinosides of malvidin and petunidin showed the greatest decrease. Addition of yeast improved the stability of the anthocyanins. In contrast to anthocyanins, quercetin, quercetin-3-glucoside and detected phenolic acids were relatively stable. Antioxidative capacity and total phenolic content decreased in all samples. In conclusion, dietary supplementation of rosehips from Rosa pimpinellifolia or bilberry suppressed oxidative stress in colonic tissue of mice. Protective effects may be due to the high anthocyanin content, presence of phenolic metabolites and changed microflora. Addition of LAB improved status of the colonic but not the ileal tissue.