The aim of this work was to investigate in vitro the quenching activity of green tea polyphenols against alpha,beta-unsaturated aldehyde, using 4-hydroxy-nonenal (HNE) as prototype and HPLC-ESI-MS/MS techniques. HNE is the most abundant and genotoxic product of oxidation of dietary polyunsaturated fatty acids, and is believed to be involved in the early stage of colorectal carcinogenesis on account of its genotoxic potential. Both epigallocatechin gallate (EGCG, 1.0-3.5 mM), the main constituent of green tea polyphenols, and a green tea aqueous extract are able to quench HNE (50 mu M) in colorectal physiomimetic conditions (10 mM), giving rise to the formation of six diastereomeric covalent adducts at the phosphate buffer, pH 8.0, 37 degrees C), giving A of EGCG, as indicated by their ESI-MS/MS fragmentation pathways. The specificity of the adduction positions was explained by H-1 NMR experiments. HNE quenching is pH-dependent and maximum at pH 8.0. ESI-MS analysis showed no formation of 4-hydroxy-2,3-epoxy-nonanal, or adduction of the epoxide to EGCG. This implies that too little hydrogen peroxide (1 mM, 24 h incubation, FOX-2 method) develops from auto-oxidation of EGCG in our aerobic experimental conditions to oxidize HNE to its corresponding epoxide, so this mechanism is not responsible for the compound's disappearance. EGCG and green tea extract also quenched acrolein, another genotoxic alpha,beta-unsaturated aldehyde, giving one predominant adduct and minor isobaric species, probably due the adduction of acrolein at different positions of the EGCG ring A. These results suggest that EGCG and green tea extract, beside the proposed mechanisms of chemoprevention that target multiple cell-signaling pathways that control cell proliferation and apoptosis in cancer cells, can also prevent protein carbonylation in the tumor tissue environment, depending on the pH of the medium surrounding the tissue, the type of tumor, the stage of dysregulation of lipid peroxidation and, finally, the stage of carcinoma development.

Quenching of alfa, beta-unsatured aldehydes by green tea polyphenols: HPLC-ESI-MS/MS studies / G. Beretta; S. Furlanetto; L. Regazzoni; M. Zarrella; R. Maffei Facino. - In: JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL ANALYSIS. - ISSN 0731-7085. - STAMPA. - 48:(2008), pp. 606-611.

Quenching of alfa, beta-unsatured aldehydes by green tea polyphenols: HPLC-ESI-MS/MS studies

FURLANETTO, SANDRA;
2008

Abstract

The aim of this work was to investigate in vitro the quenching activity of green tea polyphenols against alpha,beta-unsaturated aldehyde, using 4-hydroxy-nonenal (HNE) as prototype and HPLC-ESI-MS/MS techniques. HNE is the most abundant and genotoxic product of oxidation of dietary polyunsaturated fatty acids, and is believed to be involved in the early stage of colorectal carcinogenesis on account of its genotoxic potential. Both epigallocatechin gallate (EGCG, 1.0-3.5 mM), the main constituent of green tea polyphenols, and a green tea aqueous extract are able to quench HNE (50 mu M) in colorectal physiomimetic conditions (10 mM), giving rise to the formation of six diastereomeric covalent adducts at the phosphate buffer, pH 8.0, 37 degrees C), giving A of EGCG, as indicated by their ESI-MS/MS fragmentation pathways. The specificity of the adduction positions was explained by H-1 NMR experiments. HNE quenching is pH-dependent and maximum at pH 8.0. ESI-MS analysis showed no formation of 4-hydroxy-2,3-epoxy-nonanal, or adduction of the epoxide to EGCG. This implies that too little hydrogen peroxide (1 mM, 24 h incubation, FOX-2 method) develops from auto-oxidation of EGCG in our aerobic experimental conditions to oxidize HNE to its corresponding epoxide, so this mechanism is not responsible for the compound's disappearance. EGCG and green tea extract also quenched acrolein, another genotoxic alpha,beta-unsaturated aldehyde, giving one predominant adduct and minor isobaric species, probably due the adduction of acrolein at different positions of the EGCG ring A. These results suggest that EGCG and green tea extract, beside the proposed mechanisms of chemoprevention that target multiple cell-signaling pathways that control cell proliferation and apoptosis in cancer cells, can also prevent protein carbonylation in the tumor tissue environment, depending on the pH of the medium surrounding the tissue, the type of tumor, the stage of dysregulation of lipid peroxidation and, finally, the stage of carcinoma development.
2008
48
606
611
G. Beretta; S. Furlanetto; L. Regazzoni; M. Zarrella; R. Maffei Facino
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/325908
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 43
  • ???jsp.display-item.citation.isi??? 41
social impact