Chemical modification of marigold (Tagetes erecta) dye via diazo-coupling reaction for enhanced dyeing on polyester: A sustainable approach

Abstract

Plant-derived natural extracts contain large amounts of polyphenolic compounds, presenting opportunities for chemical modification. The present study deals with the extraction of dye from Marigold (Tagetes erecta), a widely cultivated and commercially utilised flower, using water as an extraction medium followed by its chemical modification for sustainable synthesis of yellow dye and dyeing of polyester fabric. Phytochemical analysis and FTIR spectroscopy of the natural dye extract from Marigold flowers indicated the presence of polyphenolic flavonoids. The water-extracted natural dye was subsequently chemically modified with aniline, a primary aryl amine, via diazotisation and coupling reactions to yield a semi-synthetic natural dye with a 1.2 ± 0.3 g yield. The major constituents in the marigold natural extract and the Modified Marigold Extract (MME) dye were characterised using High-Resolution Liquid Chromatography-Mass Spectrometry (LC-HRMS). The marigold water extract contained a high concentration of Gossypetin 8-Glucoside, a yellow-coloured flavonoid compound with a mass-to-charge ratio (m/z) of 480.0904. LC-HRMS analysis further confirmed the presence of a constituent (m/z 424.0485) in the MME dye, corresponding to the predicted mass of chemically modified Gossypetin 8-Glucoside. The MME dye was subsequently employed for dyeing polyester fabric, exhibiting maximum colour strength at 10 % shade under acidic condition. The dyeing performances of the MME-dyed fabrics were evaluated in terms of fastness and post-dyeing strength. This study demonstrates a unique and novel approach to develop a yellow semi-synthetic natural dye, emphasising its potential utility for polyester dyeing.