Aims: Conjugated hydroxycinnamates, such as chlorogenic acid (caffeoyl-quinic acid), are widely consumed in a Western diet, coffee being one of the richest sources. Ingested hydroxycinnamate esters can reach the large intestine essentially unaltered, and may then be hydrolysed by esterases produced by the indigenous micro¯ora. This study is aimed at identifying bacterial species responsible for the release of natural antioxidants, such as hydroxycinnamic acids, in the human large intestine. Methods and Results: Thirty-®ve isolates recovered after anaerobic batch culture incubation of human faecal bacteria in a chlorogenic acid-based medium 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 identi®ed through genotypic characterization (16S rRNA sequencing) as Escherichia coli (three isolates), Bi®dobacterium lactis and Lactobacillus gasseri (two strains). Chlorogenic acid hydrolysing activities were essentially intracellular. These cinnamoyl esterase-producing organisms were devoid of other phenolic-degrading activities. Conclusions:The results show that certain gut bacteria, including some already recognized as potentially health-promoting (i.e. species belonging to the genera Bi®dobacterium and Lactobacillus), are involved in the release of bioactive hydroxycinnamic acids in the human colon. Signi®cance and Impact of the Study: Free hydroxycinnamates, including caffeic, ferulic and p-coumaric acids, exhibit antioxidant and anticarcinogenic properties both in vitro and in animal models. Given that the gut¯ora has a major role in human nutrition and health, some of the bene®cial effects of phenolic acids may be ascribed to the micro¯ora involved in metabolism.

Flavonoids and cinnamates are widespread phenolic secondary metabolites synthesized by plants for defensive purposes. Many foods and beverages contain high levels of phenolic compounds. Certain phenolics in the diet are particularly bioactive and have pronounced effects on mammalian cells. These effects, together with epidemiological studies and animal models, have led to the hypothesis that dietary phenolics contribute to the health benefits of a diet rich in fruit and vegetables. This paper examines the biochemistry of the uptake and metabolic route of two groups of plant phenolics, the flavonols and hydroxycinnamates.

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The ester-linked ferulic acid of wheat bran and sugar-beet pulp can be con¨erted to¨anillin using biological transformation. Free ferulic acid from sugar-beet pulp and from wheat bran was almost quantitati¨ely obtained by extensi¨e degradation of the cell-walls using enzyme mixtures complemented with specific ferulic acid esterases. The Basidiomycete Pycnoporus cinnabarinus then con¨erted the released ferulic acid to¨anillin. The selection of stable and highly producti¨e strains was achie¨ed using formal ( ) genetics. The use of cellobiose as an acti¨ator of the¨anillin pathway, and the sequential addition of a precursor ferulic acid in cultures of selected P. cinnabarinus strains, allowed 90 and 300 mg r L of¨anillin to be obtained from ferulic acid enzymically released from wheat bran and sugar-beet pulp, respecti¨ely. This process was adapted into a two-step process in¨ol¨ing two filamentous fungi, Aspergillus niger and P. cinnabarinus, with complementary capabilities of transformation.

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