The role of natural indigo dye in alleviation of genotoxicity of sodium dithionite as a reducing agent

Abstract

Indigo blue is a natural dye used for thousands of years by civilizations to dye fabric blue and it is naturally obtained from Isatis tinctoria. I. tinctoria is not only used for extraction of indigo blue color but also used medicinally in Traditional Chinese Medicine because of its active compounds. Sodium dithionite (Na 2 S 2 O 4 ) is used in dye bath for indigo blue extraction, but this reducing agent and its derivatives are major pollutants of textile industry and subsequently have hazardous influences on public health. Herein, the present study was designed to obtain the high yield of natural indigo dye but with low possible toxic effect. In this context, genotoxic effects of particular combinations of natural dye solutions obtained from Isatis tinctoria subsp. tomentolla with Na 2 S 2 O 4 as reducing agent were investigated. Dye solutions were obtained using two different pH levels (pH 9 and 11) and three different concentrations of Na 2 S 2 O 4 (2.5, 5 and 10 mg/ml). In addition to the dye solutions and reducing agent, aqueous extracts of I. tinctoria were assessed for their genotoxicity on human lymphocytes. For in vitro testing of genotoxicity, chromosomal aberrations (CAs), sister chromatid exchanges (SCEs) and mitotic indexes (MI) assays were used. Accordingly, Na 2 S 2 O 4 caused significant increases in CA and SCE as well decrease in MI but the genotoxic effects of sodium dithionite were reduced with natural indigo dye. As a result, aqueous extracts of Isatis leaves removed the toxic effects of sodium dithionite and showed anti-genotoxic effect. For the optimal and desired quality but with less toxic effects of natural dye, 2.5 mg/ml (for wool yarn) and 5 mg/ml (for cotton yarn) of Na 2 S 2 O 4 doses were found to be the best doses for reduction in the dye bath at Ph 9.

Identity blues: the ethnobotany of the indigo dyeing by Landian Yao (Iu Mien) in Yunnan, Southwest China

“…Synthetically-produced indigo was of superior quality to indigo from plants and was therefore preferred by dyers [9]. Although some indigenous communities in remote areas continue to use indigo from plants, most industrially used indigo is synthetic [10].…”

“…These include health and safety risks caused by toxic mordants and the high energy costs [11]. For example, sodium dithionite (Na 2 S 2 O 4 ) is used as a reducing agent in modern indigo dyeing processes and this reducing agent and its derivatives are major pollutants of the textile industry and have negative effects on human health [10]. In recent years, it observed an increased interest in natural dyes because of the growing awareness of the toxicity and pollution resulting from the synthetic dyes [12–14].…”

Indigo—A New Tribological Substance Class for Non-Toxic and Ecological Gliding Surfaces on Ice, Snow, and Water

“…As a gliding layer, the environmental compatibility of synthetic indigo should not be compared to its use as a textile dye, as the toxicologically and ecologically harmful reduction process with sodium dithionite is not required [ 24 , 25 ]. With synthetic instead of natural indigo, a higher yield can be reached, but the byproducts aniline and N-methylaniline are particularly problematic in terms of toxicity [ 26 ].…”

A Study on Sustainable Design for Indigo Dyeing Color in the Visual Aspect of Clothing

“…Indigo dyeing in Taiwan obtains materials from local sources that are planted and manufactured again and again. The extracted plant residue is able to make compost, and the dyeing water is used for repeated irrigation [17,18].…”