Monitoring of methylglyoxal/indole interaction by ATR-FTIR spectroscopy and qTOF/MS/MS analysis

Highlights

• Methylglyoxal can be scavenged by indole; a major degradation product of tryptophan.

• The reaction was followed by monitoring the carbonyl region by ATR-FIR spectroscopy.

• The initial adduct underwent rapid oxidation into carboxylic acid on the ATR cell.

• Proposed structures were identified by high resolution qTOF/MS/MS analysis.

Abstract

Sugar derived reactive 1,2-dicarbonyl intermediates are considered important precursors for the formation of Maillard reaction products. Efficient strategies are needed to modulate their formation in food. Indole a major thermal degradation product of tryptophan, has been shown to scavenge such 1,2-dicarbonyls at high temperatures. In this study, the trapping of methylglyoxal by indole was monitored at various temperatures either by (a) ATR-FTIR spectroscopy or (b) in-solution using qTOF/MS/MS analysis. Information obtained through these studies have indicated that even at room temperature indole can quickly react with methylglyoxal forming an adduct as confirmed by the emergence of a new peak at 1729 cm⁻¹ and by qTOF/MS/MS analysis. On the open surface of the ATR crystal this adduct underwent a fast oxidization into carboxylic acid as evidenced by the disappearance of the band at 1729 cm⁻¹ and the formation of a new band at 1712 cm⁻¹ and its subsequent conversion into a carboxylate band under basic conditions.