Malagasy Dye Plant Species: A Promising Source of Novel Natural Colorants with Potential Applications - A Review.

Due to the potentially harmful effects of some synthetic dyes, there is an increasing demand for natural colorants. Recent literature has emphasized the necessity of investigating new sources of dyes. This review discusses the biological sources of dyes derived from the rich plant diversity of Madagascar. As one of the first contributions on the use of these dyestuffs for dyeing textiles, it provides an overview of 128 dye plant species with other potential applications for coloring materials in industry. A detailed description of the botanical and chemical properties of these dyestuffs is given. We believe that the Madagascar plant diversity may be a promising source of novel colorants not yet investigated. We considered it worthwhile to carry out a thorough scientific study of a set of Malagasy plants carefully selected for their coloring properties together with their potential use and valorization in specialized industries where use of natural colorants would be a particular interest.

Towards a semiquantitative non invasive characterisation of Tyrian purple dye composition: Convergence of UV-Visible reflectance spectroscopy and fast-high temperature-high performance liquid chromatography with photodiode array detection.

In this paper, partial least square (PLS) regression is innovatively applied for a semi-quantitative non invasive study of the most precious dye of Antiquity: Tyrian purple. This original approach for the study of organic dyes in the cultural heritage field, is based on the correlation of spectrophotometric (UV-Visible) and chromatographic (Fast-HT-HPLC-PDA) data from an extensive set of textiles prepared with different snail species according to historical recipes. A cross-validated PLS model, based on the quantity of 6,6'-dibromoindigotin, displays an excellent correlation factor (R(2)Y = 0.987) between values determined by chromatography and those predicted from reflectance spectra. This indicates that the spectral features of Tyrian purple on textile fibre is strictly related to the amount of this indigoid component whose content may be non invasively predicted from reflectance spectrum. The studied correlation also highlights that, independently of the dyeing method and nature of the textile fibre used, the relative content of 6,6'-dibromindigotin may be used as a parameter to distinguish samples prepared with Hexaplex trunculus L. snails from those prepared with further mollusc species. To validate this model, archaeological textile fragments dating from the Roman period were successfully examined. The results achieved open an absolutely new way in Tyrian purple analysis in cultural heritage by non invasive spectroscopic techniques attesting their convergence with HPLC and giving them a semi-quantitative value.