Chemical analysis of selected natural dyestuffs: study of their potentional biological activity

The knowledge of the isolation and identification of natural organic dyestuffs constitutes a very important element of the natural and cultural heritage of the Mediterranean. The identification of the natural organic dyestuffs that have been used in artworks of cultural heritage is considered essential for the contribution in the certification of the work’s authenticity, for the work’s correct maintenance and for the determination of the time period that the work was created. Finally, the study of their potential biological activity offers greater interest in these dyes.The aim of the present doctoral thesis was the collection and the chemical analysis of natural organic colourants, the identification of the structure of the isolated components as well as the study of their biological activity.In the first part, dyestuffs of historical interest were studied. Thus, Cotinus coggygria Scop., Dactylopius coccus Costa, and Caesalpinia sappan L were studied. 11 colouring compounds were isolated from C. coggygria, 7 of which are reported for the first time as components of C. coggygria. 4 colouring components were isolated from C. sappan. 7 colouring components were isolated from Dactylopius coccus. 4 of them are new natural products, 3 of which are known as dcIII, dcIV, dcVII.In the second part, natural dyes of microbial origin were studied. Secondary metabolites of Malasseziz furfur strains were isolated when L-tryptophan was used as the single nitrogen source in the culture medium. The production of indole derivatives using HPLC from multiple and independent extracts of M. furfur strains that come from different skin regions and diseases, as well as the statistical analysis for the comparison of indole derivatives that were isolated by various strains of M. furfur, was investigated. Then, indirubin was isolated and quantified in various M. furfur strains. 8 metabolites were isolated, 2 of which were isolated for first time. It was also proved that:• The production of indole metabolites is regulated by factors related with the origin of each strain.• The indole derivatives were produced at statistically significant quantities by all M. furfur strains isolated from pathogenic skin compared to strains isolated from healthy skin. • The quantity of metabolites is statistically connected with the severity of the illness: Seborrhoeic dermatitis > pityriasis versicolor> dandruff >healthy.• Indolo[3,2-b]carbazole and indirubin are described for the first time as M. furfur metabolites. Both of them are potent ligands of the aryl hydrocarbon receptor (AhR).• The extractions of M. furfur are AhR activators