This is the fruit of the medicinal herb Chrozophora tinctorial and a lot of effort has been made to understand its make-up.
Medieval texts describe the practice of extracting a brilliant blue dye from the plant, which was stored as watercolour on cloth then applied as paint on many great works of European art.
Repeated efforts over two centuries to discover the molecular structure of the folium have been unsuccessful, but now a team led by Paula Nabais from Portugal’s Universidade NOVA has the answer.
And it was very much a team effort, with chemists joining forces with medieval art conservation scientists and a biologist with expertise in botany and Portuguese flora.
They consulted medieval texts to learn how best to collect C. tinctoria, gathered fruits over three summers, extracted the compound that produces the pigment, then isolated and purified it.
Using a combination of liquid and gas chromatography, mass spectrometry and nuclear magnetic resonance they determined that it represents a newly described class of dyes: it is neither an anthocyanin dye, a class found in many blue flowers and fruits, nor an indigo dye, the most stable natural blue variety of pigment.
And that’s useful knowledge if you want to preserve objects as precious as 1000-year-old manuscript illuminations.
Originally published by Cosmos as A medieval mystery solved
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.
