GC–MS detection of plant pigments and metabolites in Roman Julio-Claudian wall paintings

For the first time, plant pigments were detected in Roman frescoes. Indeed, only sporadic papers proved the application of natural hues in ancient paintings and none of them relative to Roman art. Therefore, eight differently coloured fragments of Julio-Claudian wall paintings, collected from Terme degli Stucchi Dipinti archaeological site (Rome, Italy), were subjected to GC–MS analysis, obtaining detailed chemical profiles. Vegetal dyes (ie. Indigotin, Neronine, Alizarin) or colourless metabolites ascribable to plant species (ie. Basella rubra, Sesanum radiatum, Lamium purpureum) were detected. Plant waxes, oils (ie. Brassicaceae) and resins (ie. Pinaceae) were found to be preferred as binders or protective coatings instead of animal glues (ie. collagen, egg). Several natural molecules, typically associated to plant organisms (ie. Lamiaceae and Citrus species), were also identified. These data suggest the predominant role of plant extracts in ancient art and increase the knowledge about organic materials of Roman frescoes, facilitating modern restorers’ activities.