Characterisation of catechins and their oxidised derivatives in Ceylon tea using multi-dimensional liquid chromatography and high-resolution mass spectrometry

ElsevierVolume 1682, 25 October 2022, 463477Journal of Chromatography AHighlights•

Optimisation of a method combining multi-dimensional LC and high-resolution MS.

MDLC improved chromatographic separation of oxidised catechin derivatives.

Putative identification of catechin isomers was conducted using mass loss data.

Nine oxidised catechin derivatives were detected for the first time in Ceylon tea.

Abstract

Tea is a complex food matrix comprising of many structurally diverse compounds, of which catechins and their oxidised derivatives are of particular interest due to their nutritional functionality. However, these catechins and derivatives exist in various isomeric forms with few or no pure standards available, rendering their analysis challenging. A method combining multi-dimensional liquid chromatography (MDLC) and high-resolution mass spectrometry (HRMS) was developed for the characterisation of these compounds using Ceylon tea as a model. Based on a Plackett–Burman (PB) design, flow rate and initial methanol percentage were identified as the most significant factors (p < 0.05) affecting chromatogram coverage and resolution (Rs) for comprehensive two-dimensional LC (LCxLC) and heart-cutting two-dimensional LC (LC-LC) respectively. Central composite design (CCD) was then applied using these parameters for method optimisation and to identify second-order relationships between screened parameters. The optimised LCxLC (flow rate: 2.18 mL/min and initial methanol percentage: 28.0%) and LC-LC (flow rate: 0.86 mL/min and initial methanol percentage for different cuts: A- 10.0%; B- 15.8%; and C- 18.7%) methods were applied to the analysis of Ceylon tea samples from seven regions of Sri Lanka and demonstrated an improved separation of co-eluting isomeric compounds. Finally, with the mass spectral information from HRMS, a total of 31 compounds (eight monomers, 17 dimers, five trimers and one tetramer) were detected and putatively identified in Ceylon tea.

Keywords

MDLC

HRMS

Catechins

Oxidised derivatives

Ceylon tea

Data Availability

Data will be made available on request.

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