New advanced extraction and analytical methods applied to discrimination of different lichen species used for orcein dyed yarns: Preliminary results

Development of a Combined Protein and Dye Extraction Approach for the Analysis of Keratin-Based Textiles

Archaeological textiles represent precious remains from ancient culture; this is because of the historical and cultural importance of the information that can be obtained by such relics. However, the extremely complicated state of preservation of these textiles, which can be charred, partially or totally mineralized, with heavy soil or biological contamination, requires highly specialized and sensitive analytical tools to perform a comprehensive study. Starting from these considerations, the paper presents a combined workflow that provides the extraction of dyes and keratins and keratin-associated proteins in a single step, minimizing sampling while maximizing the amount of information gained. In the first phase, different approaches were tested and two different protocols were found suitable for the purpose of the unique workflow for dyes/keratin-proteins: a slightly modified urea protocol and a recently proposed new TCEP/CAA procedure. In the second step, after the extraction, different methods of cleanup and workflow for proteins and dyes were investigated to develop protocols that did not result in a loss of aliquots of the analytes of interest and to maximize the recovery of both components from the extracting solution. These protocols investigated the application of two types of paramagnetic beads, unmodified and carboxylate-coated hydrophilic magnetic beads, and dialysis and stage-tip protocols. The newly designed protocols have been applied to cochineal, weld, orchil, kermes, and indigo keratin-based dyed samples to evaluate the effectiveness of the protocols on several dye sources. These protocols, based on a single extraction step, show the possibility of investigating dyes and keratins from a unique sample of 1 mg or lesser, with respect to the thresholds of sensitivity and accuracy required in the study of textile artifacts of historical and artistic values.

Thin layer chromatography coupled with surface enhanced Raman scattering for rapid separation and on-site detection of multi-components

The separation and detection of multi-component mixtures has always been a challenging task. Traditional detection methods often suffer from complex operation, high cost, and low sensitivity. Surface enhanced Raman scattering (SERS) technique is a high sensitivity, powerful and rapid detection tool, which can realize the specific detection of single substance components, but it must solve the problem that multi-component mixtures cannot be accurately determined. Thin layer chromatography (TLC) technology, as a high-throughput separation technology, uses chromatographic plate as the stationary phase, and could select different developing phases for separation experiments. The advantages of TLC technology in short distance and rapid separation are widely used in protein, dye and biomedical fields. However, TLC technology has limitations in detection ability and difficulty in obtaining ideal signal intensity. The combination of TLC technology and SERS technology made the operation procedure simple and the sample size small, which can achieve rapid on-site separation and quantitative detection of mixtures. Due to the rapid development of TLC-SERS technology, it has been widely used in the investigation of various complex systems. This paper reviews the application of TLC-SERS technology in food science, environmental pollution and biomedicine.

The dependence of the spectroscopic properties of orcein dyes on solvent proticity: insights from theory and experiments

The electronic spectral properties of α-hydroxy-orcein (α-HO), one of the main components of the orcein dye, have been extensively investigated in solvents of different proticity through UV-Vis spectrophotometry combined with DFT and TDDFT calculations. The results highlight the occurrence of an acid-base equilibrium between the neutral (absorption maximum at 475 nm) and the monoanionic (absorption maximum at 578 nm) forms of the molecule. The position of this equilibrium was found to be sensitively dependent on solvent proticity, solution concentration and pH. Quantum mechanical calculations support the rationalization of the experimental data, confirming the key role of the protic solvent in shifting the acid-base equilibrium, through the establishment of hydrogen bond interactions on specific functional groups of the dye. Both deprotonation and dye coordination with protic solvent molecules determine the reduction of the HOMO-LUMO energy gap (0.71 eV), that can be related with the bathochromic effect envisaged both experimentally (0.59 eV) and theoretically (0.50 eV).

HPLC Fingerprint Analysis with the Antioxidant and Cytotoxic Activities of Selected Lichens Combined with the Chemometric Calculations

The aim of this study was to evaluate the ability of multivariate techniques to predict antioxidant and cytotoxic activity of the selected lichens from the chromatographic data. A simple and reproducible HPLC-DAD technique has been used to obtain the chromatographic fingerprint profiles. Reversed phase high performance liquid chromatography (RP-HPLC) linear gradient system with methanol, water and phosphoric acid (V) (pH 2.3) as the mobile phase was used (50 min). Principal Component Analysis (PCA) has been applied to the evaluation of the phytochemical similarity between studied samples, especially between the same species collected in various places of Poland (Cetraria islandica (L.) Ach., CI, Cladina mitis Sandst., CM, Hypogymnia physodes (L.) Nyl., HP). The ability to scavenge free radicals was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods and the total phenolic content was determined by Folin-Ciocalteu (F-C) test. In the case of DPPH % of inhibition was higher for selected species (Pseudevernia furfuracea (L.) Zopf, H. physodes in comparison to the literature data. The FRAP test showed that the H. physodes extract had higher ability to scavenge free radical in comparison to Cladonia furcata (Huds.) Schrader and Evernia prunastri (L.) Ach., whereas P. furfuracea extract showed higher ability than C. islandica. The high content of phenolics in P. furfuracea and H. physodes confirms their high antioxidant activity. The cytotoxic activity of studied extracts was tested by cell culture method using the human HL-60 / MX2 acute CKL-22 (CRL-2257) promyelocytic leukemia tumor cell line. The lowest values of IC₅₀ [µg∙mL^-1] were obtained for: H. physodes (HP1)-99.4; C. digitate-122.6; H. physodes (HP)-136.5, C. subulata-142.6; C. mitis-180.2.

Effect of hydrogen bonding interaction on the photophysics of α-amino-orcein

This paper reports for the first time a detailed spectroscopic investigation into the ground- and excited-state properties of α-amino-orcein (α-AO), one of the main components of the orcein dye, in solvents of different proticity and water at different pHs. In order to gain insight into the nature of the involved transitions and excited state deactivation pathways, the study was carried out by means of UV-Visible steady state and ultrafast spectroscopic techniques with the support of quantum mechanical calculations (DFT and TDDFT). The results highlight that the photophysical and photodynamic behaviour of α-AO are highly sensitive to the solvent proticity and pH. In particular, protic environment induces a red shift (55 nm) of the absorption spectrum together with a relevant decrease of the fluorescence quantum yield (from 0.19 in acetonitrile to 6.6 × 10^-3 in methanol) and radiative rate constant (two orders of magnitude). A notable red shift is also caused by increasing the pH leading the molecule from monocationic to neutral and then monoanionic form through two deprotonation steps (pKa = 3.539 ± 0.006 and 11.180 ± 0.006). Following deprotonation, the molecule assumes spectral and photophysical properties very similar to those retrieved in protic media. The observed behaviour has been rationalized through the occurrence of hydrogen bonding, likely involving to a greater extent the carbonyl oxygen of α-AO and the protic solvent, that favours the charge delocalization on the whole chromophore as well as fast non-radiative excited state deactivation. The ultrafast spectroscopic investigation revealed in fact the presence, in protic solvent, of a short living component (tens of picoseconds), assignable to solvent complexed S₁ state, alongside the long living component (few nanoseconds) observed in aprotic media and attributed to the solvent free S₁ state. The results achieved in this study for α-AO provides an important contribution to the interpretation of absorption and fluorescence features of orcein dye mixture in more complex systems (protein based substrates within the many aspects of the cultural heritage and biomedical field) where hydrogen bonds are expected to play a crucial role in mediating the interaction with the environment.

A new high-throughput method to make a quality control on tattoo inks

Nowadays, practice of tattooing is very common worldwide and, along with this increasing trend, there is also an increased risk of adverse reactions to tattoo pigments that are well known and described in literature. Previous studies have reported that cutaneous and allergic reactions to a particular pigment can manifest in several ways (allergic contact dermatitis and photo-allergic dermatitis). In this paper, a new high-throughput method is presented, in order to achieve a new system for the quality control on tattoo inks based on chromatographic-spectroscopic approach. The samples, twenty-one tattoo inks and three permanent makeup, comprised the following colors: black inks, yellow, blue, green, white, pink and various shades of red (pigment that gives many allergic responses) were analyzed through the combination of chromatographic and spectroscopic techniques, the HPTLC-Raman. In particular, Raman technique has been chosen because of its high sensitivity towards the inorganic and organic pigments, main constituents of tattoo inks. Moreover, the advantage of this hyphenated technique is to overcome the problem of analysing the complex mixture of tattoo inks, allowing to obtain a Raman spectrum of each single component, isolated by chromatographic separation. This approach aims at developing a powerful instrument to establish the nature of tattoo inks and substances that could be cause adverse reactions in tattooed patients.