Within this project, several plants that could have been sources of yellow dyes in medieval ages (in Portugal) were collected: Anthemis spp., Carthamus tinctorius, C. lanatus, Chrysanthemum spp., Daphne gnidium, Reseda luteola, Rhamnus spp., Rhus coriaria, Serratula tinctoria, Solidago virgaurea, Prangos trifida.

Plant metabolites, including polyphenols, often vary with environmental parameters, such as altitude, or exhibit seasonal patterns related to water or light stresses in Mediterranean climate. To encompass such variation in wild plants, plant material was collected in three different sampling years. Extracts of colorant plants was analyzed by HPLC coupled to an ESI-MS. Additionally, the elaboration of a yellow chromophores database will allow for confirmation of the structures found in historical textiles.

This project has also studied the stability of yellow dyes extracted from the natural sources obtained in the task "In search of Lost yellows". The stability of the yellow colours was assessed by the quantum yields of reaction. It was possible to understand the stability scale of several flavonoid yellows, namely luteolin, luteolin-7-O-glucoside, quercetin, quercetin-3-O-glucoronide, kaempferol, eriodyctiol, and others.