HPLC monitoring of isomerization/cyclicization and redox tuning of lapachol upon attachment to palygorskite and sepiolite — ASN Events
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HPLC monitoring of isomerization/cyclicization and redox tuning of lapachol upon attachment to palygorskite and sepiolite (#139)

Josep Esteve-Romero 1 , Francisco M. Valle-Algarra 2 , Antonio Domenech-Carbó 2 , Maria-Teresa Domenech-Carbó 3 , Marcelo E. Domine 4 , José-Vicente Gimeno-Adelantado 2 , Juan Péris Vicente 1 , Samuel Carda-Broch 1
  1. Química Bioanalítica - QFA - ESTCE, Universitat Jaume I, Castelló, La Plana, Spain
  2. Química Analítica, Universitat de València, València, Spain
  3. Institut de Restauració del Patrimoni, Universitat Politécnica de València, València, Spain
  4. Instituto de Tecnología Química (ITQ), Universitat Politécnica de València, València, Spain

Pigmenting materials obtained upon attachment of organic dyes to clays by ancient Mesoamerican peoples in Pre-Columbian times can be considered as precursors of contemporary hybrid organic-inorganic materials. The study of the composition and structure of such historic materials is of interest not only by their high archaeological and ethnohistoric value, but also by their implications for modern synthesis. The occurrence of redox tuning in hybrid materials, however, is not unanimously recognized in recent literature.1 For this purpose, we have studied the lapachol-palygorskite/sepiolite system resulting from the attachment of lapachol (2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone), a naphtoquinonic dye extracted from guachupin plant (Diphysa robinoides, fam. Fabaceae), used as a colorant by ancient Mesoamerican people, to palygorskite and sepiolite, fibrous phyllosilicates of ideal compositions Si8(Mg2Al2)O20(OH)2(H2O)4·4H2O, and Si6Mg4O15(OH)2·6H2O, respectively. LC-DAD and UPLC-MS analysis of DMSO extracts from lapachol-clay specimens indicated that, upon partial removing of clay’s zeolitic water by moderate thermal treatment, abundant isomerization and oxidation reactions occur with formation of  lapachones and dehydrolapachone associated to the inorganic host.

Aknowledgements. This work has been performed by members of the microcluster Grupo de análisis científico de bienes culturales y patrimoniales y estudios de ciencia de la conservación (Ref. 1362) belonging to the Valencia International Campus of Excellence. Financial support is gratefully acknowledged from the Spanish “I+D+I MICINN” projects CTQ2011-28079-CO3-01, 02 and 03 supported by ERDEF. Also P1.1B2012-36 of UJI

References

1. Doménech-Carbó, A. et al. J. Phys. Chem. B 2006, 110, 6027-6039.

2. Doménech-Carbó, A.; et al. New J. Chem. 2009, 33, 2371-2379.