title: MALDI-TOF mass spectrometry: avoidance of artifacts and analysis of caffeine-precipitated SII thearubigins from 15 commercial black teas.
abstract: Thearubigins are the quantitatively major phenolic compounds in black tea, accounting for some 60-70% of the solids in a typical black tea infusion. MALDI-TOF mass spectra for caffeine-precipitated SII thearubigins (SII CTRs) from 15 different commercial teas support previous conclusions that SII CTRs are polyhydroxylated oligomers (rather than polymers) of catechins and catechin gallates in redox equilibrium with their quinone counterparts. Some 4500 peaks were revealed in a mass range from m/z 500 to 2100. Polyphenols are redox-susceptible and readily generate artifacts during MALDI-TOF analysis when the matrix is also redox-susceptible. Of the nine matrices evaluated, 3',4',5'-trihydroxyacetophenone (F) provided the best compromise between signal intensity and redox artifact formation.
authors.affiliation: Division of Chemical Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom.
authors.forename: J Warren
authors.initials: JW
authors.lastname: Drynan
authors.forename: Michael N
authors.initials: MN
authors.lastname: Clifford
authors.forename: Jacek
authors.initials: J
authors.lastname: Obuchowicz
authors.forename: Nikolai
authors.initials: N
authors.lastname: Kuhnert
mesh_terms: D000098:Acetophenones / Q000737:chemistry; D002110:Caffeine / Q000737:chemistry*; D002392:Catechin / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D011232:Chemical Precipitation; D005504:Food Analysis / Q000379:methods*; D007202:Indicators and Reagents / Q000737:chemistry; D010084:Oxidation-Reduction; D010636:Phenols / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D059808:Polyphenols; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013662:Tea / Q000737:chemistry*
chemical_list: D000098:Acetophenones; D007202:Indicators and Reagents; D010636:Phenols; D059808:Polyphenols; D013662:Tea; C086701:thearubigin; D002110:Caffeine; D002392:Catechin