The aqueous extract of dry onion skin waste from the ‘Dorata di Parma’ cultivar was tested as a new source of biomolecules for the production of colored and biofunctional wool yarns, through environmentally friendly dyeing procedures. Specific attention was paid to the antioxidant and UV protection properties of the resulting textiles. On the basis of spectrophotometric and mass spectrometry analyses, the obtained deep red-brown color was assigned to quercetin and its glycoside derivatives. The Folin–Ciocalteu method revealed good phenol uptakes on the wool fiber (higher than 27% for the textile after the first dyeing cycle), with respect to the original total content estimated in the water extract (78.50 ± 2.49 mg equivalent gallic acid/g onion skin). The manufactured materials showed remarkable antioxidant activity and ability to protect human skin against lipid peroxidation following UV radiation: 7.65 ± 1.43 (FRAP assay) and 13.60 (ORAC assay) mg equivalent trolox/g textile; lipid peroxidation inhibition up to 89.37%. This photoprotective and antioxidant activity were therefore ascribed to the polyphenol pool contained in the outer dried gold skins of onion. It is worth noting that citofluorimetric analysis demonstrated that the aqueous extract does not have a significative influence on cell viability, neither is capable of inducing a proapoptotic effect.

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To improve the loadability and antioxidant properties of wool impregnated with onion skin extract, the introduction of SB3-14 surfactant in the dyeing process was evaluated. A preliminary investigation on the surfactant–quercetin interaction indicated that the optimal conditions for dye solubility, stability, and surfactant affinity require double-distilled water (pH = 5.5) as a medium and SB3-14 in a concentration above the c.m.c. (2.5 × 10−3 M). The absorption profile of textiles showed the flavonoid absorption band (390 nm) and a bathochromic feature (510 nm), suggesting flavonoid aggregates. The higher absorbance for the sample dyed with SB3-14 indicated greater dye uptake, which was further confirmed by HPLC analysis. The Folin–Ciocalteu method was applied to evaluate the total phenol content (TPC) released from the treated wool, while the assays FRAP, DPPH, ABTS, and ORAC were applied to evaluate the corresponding total antioxidant activity (TAC). Higher TPCs (about 20%) and TACs (5–55%) were measured with SB3-14, highlighting textiles with improved biofunctional properties. Spectrophotometric analyses were also performed with an artificial sweat. The potential cytotoxic effect of SB3-14 in both monomeric and aggregated forms, cell viability, and induction of apoptosis were evaluated in RAW 264.7 cells. These analyses revealed that SB3-14 is safe at concentrations below the c.m.c.

In this study, we were interested in comparing the amino acid profile in a specific variety of onion, Rossa da inverno sel. Rojo Duro, produced in two different Italian sites: the Cannara (Umbria region) and Imola (Emilia Romagna region) sites. Onions were cultivated in a comparable manner, mostly in terms of the mineral fertilization, seeding, and harvesting stages, as well as good weed control. Furthermore, in both regions, the plants were irrigated by the water sprinkler method and subjected to similar temperature and weather conditions. A further group of Cannara onions that were grown by micro-irrigation was also evaluated. After the extraction of the free amino acid mixture, an ion-pairing reversed-phase high performance liquid chromatography-evaporative light scattering detector (IP-RP HPLC-ELSD) method allowed for the separation and detection of almost all the standard proteinogenic amino acids. However, only the peaks corresponding to leucine (Leu), phenylalanine (Phe), and tryptophan (Trp), were present in all the investigated samples and they were unaffected from the matrix interfering peaks. The use of the beeswarm/box plots revealed that the content of Leu and Phe were markedly influenced by the geographical origin of the onions (with *** p << 0.001 for Phe), but not by the irrigation procedure. The applied HPLC method was validated in terms of the specificity, the linearity (a logarithm transformation was applied for the method linearization), the limit of detection (LOD) and limit of quantification (LOQ), the accuracy (≥90% for inter-day Recovery percentage), and the precision (≤10.51 for the inter-day RSD percentage), before the quantitative assay of Leu, Phe, and Trp in the onion samples. These preliminary findings are a good starting point for considering the quantity of the specific amino acids in the Rossa da inverno sel. Rojo Duro variety as a fingerprint of its geographical origin.

Carnosine is present in high concentrations in specific human tissues such as the skeletal muscle, and among its biological functions, the remarkable scavenging activity toward reactive carbonyl species is noteworthy. Although the two enantiomers show almost identical scavenging reactivity toward reactive carbonyl species, only d-carnosine is poorly adsorbed at the gastrointestinal level and is stable in human plasma. Direct methods for the enantioselective analysis of carnosine are still missing even though they could find more effective applications in the analysis of complex matrices. In the present study, the use of two different chiral stationary phases is presented. A chiral ligand-exchange chromatography stationary phase based on N,S-dioctyl-d-penicillamine resulted in the direct enantioseparation of carnosine. Indeed, running the analysis at 25°C and 1.0 mL/min with a 1.5 mM copper(II) sulfate concentration allowed us to obtain separation and resolution factors of 3.37 and 12.34, respectively. However, the use of a copper(II)-containing eluent renders it hardly compatible with mass spectrometry detectors. With the teicoplanin-based stationary phase, a mass spectrometry compatible method was successfully developed. Indeed, a water/methanol 60:40 v/v pH 3.1 eluent flowed at 1.0 mL/min and with a 25°C column temperature produced separation and resolution factors of 2.60 and 4.16, respectively.