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Papers by jacek obuchowicz

Rapid Communications in Mass Spectrometry, 2010

Thearubigins are the most abundant group of phenolic pigments found in black tea, accounting for ... more Thearubigins are the most abundant group of phenolic pigments found in black tea, accounting for an estimated 60-70% of the solids in a typical black tea infusion. Fifty years ago the term thearubigins was first introduced and to date the chemical nature of the thearubigins remains largely unresolved, if not mysterious, despite numerous attempts made to clarify their structure. Thearubigins isolated from 15 commercial black teas have been analyzed using a strategy combining standard chemical characterization along with a series of modern complementary mass spectrometry techniques, including MALDI-TOF-MS, FTICR-MS, LC/TOF-MS and LC/MS/MS. Fifteen molecular formulas have been matched to constituents of fresh tea leaf that have survived processing and 21 to dimeric transformation products such as theasinensins, theaflavins, theaflavates, theanaphthoquinones, theacitrins and oolongtheanins, which were further confirmed by ESI MS/MS. MALDI-TOF-MS data revealed an average of 5000 additional thearubigin components in the mass range between m/z 1000 to 2100 clearly defining the molecular weight range of the thearubigin fraction. Six selected samples have for the first time been analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). FT-ICR-MS data revealed the presence of a maximum of 9428 peaks in the mass range 300 to 1000 m/z and molecular formulas were assigned to 1517 of them. Data interpretation strategies developed for petrolomics studies (van Krevelen and Kendrick analyses) have for the first time been applied to black tea thearubigins and a novel interpretation protocol has been developed to refine these procedures for the investigation of complex mixtures, leading to a novel hypothesis for the formation and structure of the black tea thearubigins named oxidative cascade hypothesis.

Natural Product Reports, 2010

This review summarises the chemistry of low molecular weight polyphenols isolated and characteris... more This review summarises the chemistry of low molecular weight polyphenols isolated and characterised from black tea, discussing both structures identified and mechanisms of their likely formation.

Journal of Agricultural and Food Chemistry, 2012

Thearubigins are the quantitatively major phenolic compounds in black tea, accounting for some 60... more 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.

Journal of Agricultural and Food Chemistry, 2013

Journal of Food Composition and Analysis, 2011

A worldwide data collection was undertaken using the validated ISO methods ISO 14502 parts 1 and ... more A worldwide data collection was undertaken using the validated ISO methods ISO 14502 parts 1 and 2, with 17 laboratories participating worldwide. This is the largest tea database worldwide, containing 295 black- and 358 green-origin teas. We found it quite easy to differentiate most green and black teas by the type of analysis presented in this study. The geographic spread

PURPOSE: To increase the adhesion to a substrate, improve resistance to wear and contrive to impr... more PURPOSE: To increase the adhesion to a substrate, improve resistance to wear and contrive to improve a system performance by a method wherein a disperse phase containing a water insoluble heat softenable component and a layer containing a binder made of a component soluble in an aqueous alkaline medium are provided. CONSTITUTION: By covering a substrate with a substance transferable to a disperse as heat, a radiation sensitive plate is obtained. Next, by directing a radiation to a covering continuous region, the radiation is adjusted so as to selectively and locally fuse the covering particles in order to expose the radiation sensitive plate with a high tenacity radiation beam in response to an image. The, the image exposed plate is developed with an aqueous medium so as to selectively remove a region containing un-fused particles and consequently leave the image, which is formed through the locally fused particles, on the substrate. Further, the developed plate is heated and expose...

Rapid Communications in Mass Spectrometry, 2010

Thearubigins are the most abundant group of phenolic pigments found in black tea, accounting for ... more Thearubigins are the most abundant group of phenolic pigments found in black tea, accounting for an estimated 60-70% of the solids in a typical black tea infusion. Fifty years ago the term thearubigins was first introduced and to date the chemical nature of the thearubigins remains largely unresolved, if not mysterious, despite numerous attempts made to clarify their structure. Thearubigins isolated from 15 commercial black teas have been analyzed using a strategy combining standard chemical characterization along with a series of modern complementary mass spectrometry techniques, including MALDI-TOF-MS, FTICR-MS, LC/TOF-MS and LC/MS/MS. Fifteen molecular formulas have been matched to constituents of fresh tea leaf that have survived processing and 21 to dimeric transformation products such as theasinensins, theaflavins, theaflavates, theanaphthoquinones, theacitrins and oolongtheanins, which were further confirmed by ESI MS/MS. MALDI-TOF-MS data revealed an average of 5000 additional thearubigin components in the mass range between m/z 1000 to 2100 clearly defining the molecular weight range of the thearubigin fraction. Six selected samples have for the first time been analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). FT-ICR-MS data revealed the presence of a maximum of 9428 peaks in the mass range 300 to 1000 m/z and molecular formulas were assigned to 1517 of them. Data interpretation strategies developed for petrolomics studies (van Krevelen and Kendrick analyses) have for the first time been applied to black tea thearubigins and a novel interpretation protocol has been developed to refine these procedures for the investigation of complex mixtures, leading to a novel hypothesis for the formation and structure of the black tea thearubigins named oxidative cascade hypothesis.

Natural Product Reports, 2010

This review summarises the chemistry of low molecular weight polyphenols isolated and characteris... more This review summarises the chemistry of low molecular weight polyphenols isolated and characterised from black tea, discussing both structures identified and mechanisms of their likely formation.

Journal of Agricultural and Food Chemistry, 2012

Thearubigins are the quantitatively major phenolic compounds in black tea, accounting for some 60... more 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.

Journal of Agricultural and Food Chemistry, 2013

Journal of Food Composition and Analysis, 2011

A worldwide data collection was undertaken using the validated ISO methods ISO 14502 parts 1 and ... more A worldwide data collection was undertaken using the validated ISO methods ISO 14502 parts 1 and 2, with 17 laboratories participating worldwide. This is the largest tea database worldwide, containing 295 black- and 358 green-origin teas. We found it quite easy to differentiate most green and black teas by the type of analysis presented in this study. The geographic spread

PURPOSE: To increase the adhesion to a substrate, improve resistance to wear and contrive to impr... more PURPOSE: To increase the adhesion to a substrate, improve resistance to wear and contrive to improve a system performance by a method wherein a disperse phase containing a water insoluble heat softenable component and a layer containing a binder made of a component soluble in an aqueous alkaline medium are provided. CONSTITUTION: By covering a substrate with a substance transferable to a disperse as heat, a radiation sensitive plate is obtained. Next, by directing a radiation to a covering continuous region, the radiation is adjusted so as to selectively and locally fuse the covering particles in order to expose the radiation sensitive plate with a high tenacity radiation beam in response to an image. The, the image exposed plate is developed with an aqueous medium so as to selectively remove a region containing un-fused particles and consequently leave the image, which is formed through the locally fused particles, on the substrate. Further, the developed plate is heated and expose...