Abstract
Safflower (Carthamus tinctorius L.) petals, depending on the nature of a dyeing bath, dye fibers yellow or red. This is due to the presence of two kinds of components, water-soluble yellow colorants and alkali-soluble red compounds. In this study, safflower-yellow- and safflower-red-dyed silk, cotton, and wool fibers were investigated using high- or ultrahigh-performance liquid chromatography hyphenated with spectrophotometry and tandem mass spectrometry (HPLC–UV–vis–ESI-MS/MS) and high-resolution Orbitrap mass spectrometry (HPLC–HESI-HRMS) in order to identify the natural dye in historical textiles. This way, several quinochalcone C-glycosides were separated and characterized. Their low- and high-resolution MS/MS spectra expanded the database of natural colorants in cultural heritage objects. Moreover, the colorless ct-markers (with a hitherto unknown structure) present in all safflower-dyed fabrics, regardless of the color or preservation conditions, were revealed to be E/Z stereoisomers of N1,N5,N10-tri-p-coumaroylspermidine. Since most of the standards was not available, discussion on possible molecular structures was provided. As a consequence, the analytical investigation of the reference fibers dyed with safflower demonstrated that the dye composition varies, depending on the dyeing conditions and type of fiber. Moreover, it was proven that carthamin, although alkali soluble, can be successfully released with a mild extraction method, without its hydrolysis under these conditions. The results helped us to characterize threads sampled from 16th to 18thcentury textiles of European and Near Eastern origin. It has completed the picture of natural dyes used in the most valuable textiles availed in liturgical vestments from the collections of Krakow churches.
Highlights
The high- and low-resolution MS/MS spectra were used to update the database of markers for the identification of natural dyes in historical and archeological objects
Unavailable compounds were identified based on tandem mass spectrometry (MS/MS) experiments
The result presented in this paper provide a new knowledge regarding the tandem mass spectrometric detection of safflower components
Summary
Safflower (Carthamus tinctorius L.), a native of the arid areas having seasonal rains from Egypt to India, has been known and cultivated since antiquity.− It was used for dyeing red in China as early as the Zhou (1046−256 BC) dynasty and the Han (202 BC-220 AD) dynasty, in Japan at least in the second century BC, and in Persia in the sixth century BC. since the safflower red colors (sometimes pinks), bright and beautiful, were very transitory, initial baths of yellow dyes were used prior to the essential dyeing stage. safflower was used in combination with. Safflower was used on silk, cotton, and linen for dyeing red and on silk and wool to obtain yellow colors.. This work provides a detailed and comprehensive study on safflower-dyed fibers (silk, cotton, and wool) by the use of HPLC-UV−vis−ESI-MS/MS and UPLC−HESI-HRMS/MS It led to the structure elucidation of six colorless markers (formerly known as ct compounds), as well as to identification of other compounds (ten quinochalcones and nine other compounds) extracted from dyed fibers. Safflower petals bundled up in a mesh pouch were immersed in cold water and left to soak for 1 h, squeezing periodically After this time the pouch with petals was taken out from the yellow solution and squished several times to drain from it the rest of the solvent with coloring components; the received solution (dyeing bath 1) was used to dye yellow later on. Safflower-dyed fibers and historical samples were extracted using the procedure proposed by Lech, mostly with the water−methanol−formic acid method (50 μL of the mixture (8:9:3, v/v/v); 20 min of ultrasounds, 25 min in 60 °C; dilution with 50 μL of a methanol−water mixture (9:8, v/v)); only two green historical fibers were extracted with the DMSO method (50 μL of DMSO; 10 min of ultrasounds, 20 min in 60 °C; dilution with 50 μL of methanol)
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