The effects of polyphenols against oxidative stress in are determined by coexisting bacteria.

Introduction: Increasing evidence supports the role of gut microbiota in many aspects of human health, including immune, metabolic and neurobehavioral traits. Several studies have focused on how different components of the diet, such as polyphenols, can modulate the composition and function of the gut microbiota leading to health benefits.

Methods: The effects on the resistance against thermally induced oxidative stress of grown in the presence of flavonoids (quercetin or epicatechin) and fed different probiotic strains, namely CLC17, NCIMB 8809 and CECT 410, were explored.

Results: Feeding with the assayed bacteria in the absence of flavonoids did not significantly affect body size and fertility of the worms neither improve their resistance against oxidative stress compared to controls. However, increased resistance to stress was found when was cultivated in the presence of both and flavonoids, but not with or . An exploratory study revealed the presence of glycosylated and sulfated metabolites together with the aglycone in worms treated with quercetin and fed any of the different assayed LAB strains. However, in the assays with epicatechin a differential metabolite, tentatively identified as 5-(4'-hydroxyphenyl)-γ-valerolactone 3'--glucoside, was detected in the worms fed but not with the other bacteria.

Conclusion: The obtained results indicated that the interactions bacteria/polyphenol play a key role in the effects produced in regarding resistance against oxidative stress, although those effects cannot be only explained by the ability of bacteria to metabolize polyphenols, but other mechanisms should also be involved.