In vitro antioxidant activity of cotton fabric treated with ethanol and water Thymus serpyllum L. (wild thyme) extracts

The plants contain a large number of various compounds that exhibit significant antioxidant activity. Among them, polyphenols and flavonoids are the most studied compounds with different biological properties, including antioxidant activity. The functionalization of cotton fabric with natural compounds from plants results in the material with improved antioxidative properties. In this study, cotton fabrics treated with ethanol and water Thymus serpyllum L. (wild thyme) extracts were investigated in terms of antioxidant properties and chemical composition. In vitro antioxidant capacity of ethanol and water extracts, and the cotton fabric before and after functionalization was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH•), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS•+) radicals scavenging capacity assays. FTIR and UV–Vis spectroscopy elucidated the structure of the cotton fabric, extracts, and functionalized cotton fabric. FTIR spectroscopy demonstrated that the structure of cellulose was dominated in cotton, and also proved the presence of a low percentage of protein, pectin, oil, fat, and wax, as well as, binding of compounds from the extract by cross-linking with long chains of structure cotton. In dry extracts, the presence of various chemical functional groups was confirmed. UV-Vis analysis identified the active components in T. serpyllum extracts. Namely, absorption values for both spectra (water and ethanol samples) at 215-253 nm, 263-384 nm, are specific for phenolic acids, and flavonoids. Also, one of the aims of the study was to investigate the influence of various extracts (water and ethanol samples) on the antioxidant activity of cotton fabric. All extracts demonstrated excellent antioxidant properties, more potent than the reference antioxidant (ascorbic acid) in both antioxidant assays (between 85-86% in DPPH and 94-96% in ABTS assays). Pure T. serpyllum water extract was the most potent in the DPPH assay (86%), while pure ethanolic extract was the most potent antioxidant in the ABTS assay (96%). The antioxidant capacity of raw cotton fabric was insufficient (4%). On the other hand, in the DPPH assay, samples of cotton fabric with extract showed moderate activity with scavenging activity of 48% and 45% for ethanol and water extracts, respectively. Additionally, in the ABTS assay, the antioxidant activity of treated cotton fabric was 51% and 46% for ethanol and water extracts, respectively