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Identification of unknown colorants in pre-Columbian textiles dyed with American cochineal (Dactylopius coccus Costa) using high-performance liquid chromatography and tandem mass spectrometry.

Lech K, Witkoś K, Wileńska B, Jarosz M - Anal Bioanal Chem (2014)

Bottom Line: The present study concerns the identification of nine thus-far unknown derivatives of carminic acid extracted from pre-Columbian Peruvian textiles dyed with American cochineal-these derivatives are not found in commercially available preparations of the dye.This is accompanied by the elimination of H2O as well as the further loss of 60 Da from the hexoside moiety.Moreover, other losses from the carbonyl groups (44 Da from CO2 loss, 62 Da from ethylene glycol loss, 32 Da from O2 loss, 138 Da from hydroxybenzoic acid, and 120 Da from oxomethylene cyclohexadienone) provided more specific information about structures of the identified derivatives of carminic acid.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Chemistry, Chair of Analytical Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664, Warsaw, Poland.

ABSTRACT
The present study concerns the identification of nine thus-far unknown derivatives of carminic acid extracted from pre-Columbian Peruvian textiles dyed with American cochineal-these derivatives are not found in commercially available preparations of the dye. These compounds probably represent a unique fingerprint of dyed textiles from this region, as they have never been reported to occur in other fabrics of historical value. They were separated by reversed-phase high-performance liquid chromatography (phenyl column) and detected using a UV/vis spectrophotometer and two tandem mass spectrometers. Peaks observed in chromatograms registered at 450 and 500 nm were further identified by ESI QqQ MS (mainly in the negative ion mode), supported by high-resolution ESI QIT/ToF MS data. The characteristic fragmentation pathways of isolated carminic acid and its derivatives provided additional information concerning lost neutrals and thus the functional groups and substituents present in the parent molecules. This information mainly related to multiple cleavages of the hexoside moiety (initially cross-ring cleavage), which are characteristic of C-glucosides (loss of 90, 120, and 148 Da). This is accompanied by the elimination of H2O as well as the further loss of 60 Da from the hexoside moiety. Moreover, other losses from the carbonyl groups (44 Da from CO2 loss, 62 Da from ethylene glycol loss, 32 Da from O2 loss, 138 Da from hydroxybenzoic acid, and 120 Da from oxomethylene cyclohexadienone) provided more specific information about structures of the identified derivatives of carminic acid.

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Proposed mechanism for the fragmentation of the m/z 611 ion from dc7
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Sch2: Proposed mechanism for the fragmentation of the m/z 611 ion from dc7

Mentions: The quasi-molecular [M − H]− ion of dc7 is registered at m/z 611 (611.1037 in the high-resolution mass spectrum), corresponding to an elemental composition of C29H23O15, identical to the composition of dc9. It can therefore be identified as an isomer of dc9, but these molecules show different MS/MS spectra and that obtained for dc7 is substantially poorer. In it, only two relatively intense signals at m/z 429 and 309 are observed. The absence of a peak corresponding to the loss of a 44-Da fragment, as well as a difference of C7H4O2 (a benzoate group) between the elemental compositions of carminic acid and dc7, indicate that the carboxyl group is esterified by hydroxybenzoic acid. A similar phenomenon—a lack of detachment of CO2 from the hydroxybenzoic carboxylic group (not engaged in bonding)—has already been reported for diesters of aliphatic dicarboxylic acids with hydroxybenzoic acid [29]. Assuming such a structure for dc7, the formation of ions at m/z 429 (obs. m/z 429.0809, diff. for C21H18O10 4.19) can be explained by atypical detachment of the carbophenoxy ester group together with the neighboring hydroxyl group (182 Da, C8H6O5), which probably originates from a charge-remote mechanism based on the elimination of CO2, H2O, and the hydroxybenzoic acid moiety (Scheme 2).Scheme 2


Identification of unknown colorants in pre-Columbian textiles dyed with American cochineal (Dactylopius coccus Costa) using high-performance liquid chromatography and tandem mass spectrometry.

Lech K, Witkoś K, Wileńska B, Jarosz M - Anal Bioanal Chem (2014)

Proposed mechanism for the fragmentation of the m/z 611 ion from dc7
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4305107&req=5

Sch2: Proposed mechanism for the fragmentation of the m/z 611 ion from dc7
Mentions: The quasi-molecular [M − H]− ion of dc7 is registered at m/z 611 (611.1037 in the high-resolution mass spectrum), corresponding to an elemental composition of C29H23O15, identical to the composition of dc9. It can therefore be identified as an isomer of dc9, but these molecules show different MS/MS spectra and that obtained for dc7 is substantially poorer. In it, only two relatively intense signals at m/z 429 and 309 are observed. The absence of a peak corresponding to the loss of a 44-Da fragment, as well as a difference of C7H4O2 (a benzoate group) between the elemental compositions of carminic acid and dc7, indicate that the carboxyl group is esterified by hydroxybenzoic acid. A similar phenomenon—a lack of detachment of CO2 from the hydroxybenzoic carboxylic group (not engaged in bonding)—has already been reported for diesters of aliphatic dicarboxylic acids with hydroxybenzoic acid [29]. Assuming such a structure for dc7, the formation of ions at m/z 429 (obs. m/z 429.0809, diff. for C21H18O10 4.19) can be explained by atypical detachment of the carbophenoxy ester group together with the neighboring hydroxyl group (182 Da, C8H6O5), which probably originates from a charge-remote mechanism based on the elimination of CO2, H2O, and the hydroxybenzoic acid moiety (Scheme 2).Scheme 2

Bottom Line: The present study concerns the identification of nine thus-far unknown derivatives of carminic acid extracted from pre-Columbian Peruvian textiles dyed with American cochineal-these derivatives are not found in commercially available preparations of the dye.This is accompanied by the elimination of H2O as well as the further loss of 60 Da from the hexoside moiety.Moreover, other losses from the carbonyl groups (44 Da from CO2 loss, 62 Da from ethylene glycol loss, 32 Da from O2 loss, 138 Da from hydroxybenzoic acid, and 120 Da from oxomethylene cyclohexadienone) provided more specific information about structures of the identified derivatives of carminic acid.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Chemistry, Chair of Analytical Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664, Warsaw, Poland.

ABSTRACT
The present study concerns the identification of nine thus-far unknown derivatives of carminic acid extracted from pre-Columbian Peruvian textiles dyed with American cochineal-these derivatives are not found in commercially available preparations of the dye. These compounds probably represent a unique fingerprint of dyed textiles from this region, as they have never been reported to occur in other fabrics of historical value. They were separated by reversed-phase high-performance liquid chromatography (phenyl column) and detected using a UV/vis spectrophotometer and two tandem mass spectrometers. Peaks observed in chromatograms registered at 450 and 500 nm were further identified by ESI QqQ MS (mainly in the negative ion mode), supported by high-resolution ESI QIT/ToF MS data. The characteristic fragmentation pathways of isolated carminic acid and its derivatives provided additional information concerning lost neutrals and thus the functional groups and substituents present in the parent molecules. This information mainly related to multiple cleavages of the hexoside moiety (initially cross-ring cleavage), which are characteristic of C-glucosides (loss of 90, 120, and 148 Da). This is accompanied by the elimination of H2O as well as the further loss of 60 Da from the hexoside moiety. Moreover, other losses from the carbonyl groups (44 Da from CO2 loss, 62 Da from ethylene glycol loss, 32 Da from O2 loss, 138 Da from hydroxybenzoic acid, and 120 Da from oxomethylene cyclohexadienone) provided more specific information about structures of the identified derivatives of carminic acid.

Show MeSH
Related in: MedlinePlus