Identification of Red Madder and Insect Dyes by Thin-Layer Chromatography
1989; American Chemical Society; Linguagem: Inglês
10.1021/bk-1989-0410.ch013
ISSN1947-5918
Autores Tópico(s)Chromatography in Natural Products
ResumoRed natural anthraquinone dyes on ancient textile materials can be readily identified by thin-layer chromatography (TLC) if they belong to the class of madder dyes. The method also shows which type of dye plant from the family Rubiaceae has been used for dyeing (Rubia tinctorum L., R. peregrina L., R. cordifolia L., R. akane, various Galium spp., Relbunium spp., Morinda spp., Oldenlandia spp., Coprosma spp., or Ventilago spp. (Rhamnaceae) ). Any changes in the composition of the dyes during its extraction from the dyed material, e.g. the transition from pseudopurpurin to purpurin, can be prevented by suitable preparation of the sample before TLC. The red insect dyes from Dactylopius coccus COSTA (American cochineal), Kermococcus vermilio PLANCHON (kermes), and Kerria lacca KERR (lac dye) can also be readily distinguished by thin-layer chromatographic comparison. Porphyrophora polonica L. (Polish cochineal) contains small amounts of the kermes dyes kermesic acid and flavokermesic acid besides the cochineal dye carminic acid. These secondary components cannot be identified unless they have previously been concentrated. Porphyrophora hameli BRANDT (Armenian cochineal) contains nearly exclusively carminic acid. It has been reported that high-performance liquid chromatography (HPLC) has also identified a trace of kermesic acid, but TLC has not provided any clear proof of the presence of this secondary component in Armenian cochineal, even after previous concentration.
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