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In a previous study, lactic acid bacteria were isolated from meconium obtained from healthy neonates born by cesarean section. Such a finding suggested that term fetuses are not completely sterile, and that a mother-to-child efflux of commensal bacteria may exist. Therefore, presence of such bacteria in umbilical cord blood of healthy neonates born by elective cesarean section was investigated. The blood samples were submitted to an enrichment step and then inoculated onto agar plates. All the identified isolates belonged to the genus Enterococcus, Streptococcus, Staphylococcus, or Propionibacterium. Later, a group of pregnant mice were orally inoculated with a genetically labeled E. faecium strain previously isolated from breast milk of a healthy woman. The labeled strain could be isolated and polymerase chain reaction detected from the amniotic fluid of the inoculated animals. In contrast, it could not be detected in the samples obtained from a noninoculated control group.

Quercetin is a common antioxidant flavonoid found in vegetables, which is usually present in glycosylated forms, such as quercitrin (3-rhamnosylquercetin). Previous in vitro experiments have shown that quercetin exerts a bigger effect than quercitrin in the down-regulation of the inflammatory response. However, such results have not been reproduced in in vivo experimental models of intestinal inflammation, in which quercetin did not show beneficial effects while its glycosides, quercitrin or rutin, have demonstrated their effectiveness. In this study, we have reported that the in vivo effects of quercitrin in the experimental model of rat colitis induced by dextran sulfate sodium can be mediated by the release of quercetin generated after glycoside's cleavage by the intestinal microbiota. This is supported by the fact that quercetin, but not quercitrin, is able to down-regulate the inflammatory response of bone marrow-derived macrophages in vitro. Moreover, we have demonstrated that quercetin inhibits cytokine and inducible nitric oxide synthase expression through inhibition of the NF-jB pathway without modification of c-Jun N-terminal kinase activity (both in vitro and in vivo). As a conclusion, our report suggests that quercitrin releases quercetin in order to perform its anti-inflammatory effect which is mediated through the inhibition of the NF-jB pathway.

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