Abstract
The potential of Lactobacillus johnsonii NCC 533 to metabolize chlorogenic acids from green coffee extract was investigated. Two enzymes, an esterase and a hydroxycinnamate decarboxylase (HCD), were involved in this biotransformation. The complete hydrolysis of 5-caffeoylquinic acid (5-CQA) into caffeic acid (CA) by L. johnsonii esterase occurred during the first 16 h of reaction time. No dihydrocaffeic acid was identified in the reaction mixture. The decarboxylation of CA into 4-vinylcatechol (4-VC) started only when the maximum concentration of CA was reached (10 μmol/ml). CA was completely transformed into 4-VC after 48 h of incubation. No 4-vinylphenol or other derivatives could be identified in the reaction media. In this study we demonstrate the capability of L. johnsonii to transform chlorogenic acids from green coffee extract into 4-VC in two steps one pot reaction. Thus, the enzymatic potential of certain lactobacilli might be explored to generate flavor compounds from plant polyphenols.
Highlights
Polyphenols have been reported to exert a variety of biological activities, such as free radical scavenging, metal chelating and modulation of enzyme activity (Sud’ina 1993)
After 24 h of reaction time, the concentration of CA decreased and 4-VC was produced (7.5 μmol/ml). These results suggest that chlorogenic acids were hydrolyzed by L. johnsonii esterase into quinic and caffeic acids and CA was transformed into 4-VC by a hydroxycinnamic acid decarboxylase (HCD) (Figure 1)
Several other studies reported on the decarboxylation of hydroxycinnamic acids into vinyl phenols by bacteria and yeasts (Plumb 1999; Huang 1994; Hashidoko 2001; Rodriguez 2008; Curiel 2010)
Summary
Polyphenols have been reported to exert a variety of biological activities, such as free radical scavenging, metal chelating and modulation of enzyme activity (Sud’ina 1993). Chlorogenic acids are common in vegetables, the largest amounts are present in coffee (Clarke 1987). These phenolic acids are toxic to some but not all microorganisms. In a previous study we demonstrated the ability of L. johnsonii to hydrolyze rosmarinic acid into caffeic and 3,4dihydroxyphenyllactic acids (Bel-Rhlid 2009). We investigated the in vitro incubation of green coffee extract with L. johnsonii to hydrolyze chlorogenic acids into corresponding hydroxycinnamic acids. These phenolic compounds could be transformed into corresponding vinylphenols by decarboxylase activity
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