Isolation and characterization of human colonic bacteria able to hydrolysechlorogenic acid

Aims: Conjugated hydroxycinnamates, such as chlorogenic acid (caffeoyl-quin ic acid), are widely consumed in a Western diet, coffee being one of the ri chest sources. Ingested hydroxycinnamate esters can reach the large intesti ne essentially unaltered, and may then be hydrolysed by esterases produced by the indigenous microflora. This study is aimed at identifying bacterial species responsible for the release of natural antioxidants, such as hydrox ycinnamic acids, in the human large intestine. Methods and Results: Thirty-five isolates recovered after anaerobic batch c ulture incubation of human faecal bacteria in a chlorogenic acid-based medi um were screened for cinnamoyl esterase activity. Six isolates released the hydroxycinnamate, ferulic acid, from its ethyl ester in a plate-screening assay, and these were identified through genotypic characterization (16S rR NA sequencing) as Escherichia coli (three isolates), Bifidobacterium lactis and Lactobacillus gasseri (two strains). Chlorogenic acid hydrolysing acti vities were essentially intracellular. These cinnamoyl esterase-producing o rganisms were devoid of other phenolic-degrading activities. Conclusions: The results show that certain gut bacteria, including some alr eady recognized as potentially health-promoting (i.e. species belonging to the genera Bifidobacterium and Lactobacillus), are involved in the release of bioactive hydroxycinnamic acids in the human colon. Significance and Impact of the Study: Free hydroxycinnamates, including caf feic, ferulic and p-coumaric acids, exhibit antioxidant and anticarcinogeni c properties both in vitro and in animal models. Given that the gut flora h as a major role in human nutrition and health, some of the beneficial effec ts of phenolic acids may be ascribed to the microflora involved in metaboli sm.