Exploring sustainable technique on natural dye extraction from native plants for textile: identification of colourants, colourimetric analysis of dyed yarns and their antimicrobial evaluation

Use of natural dyes in textile colouration is gaining popularity all over the world during the last decade. The current study deals with solvent extraction of natural dyes from two plant species (Saraca asoca and Albizia lebbeck), statistical analyses, dyeing techniques, identification of colour components and their potential antimicrobial properties against common human pathogens. The principal colour compounds such as flavonoids and tannin moieties have been isolated from two plant extracts and identified based on chemical and spectroscopic investigations. The absorption of dyes on silk yarns was obtained from 26.65 to 39.68% at 5% concentration of dye solution. The colour strength (K/S), CIELab values and fastness properties of the dyed samples were assessed. The colour strength was enhanced with increase in dye absorbance and the mordant used. Antimicrobial studies indicated that these natural dyes possess antimicrobial activity both in solution and substrate. The dyed silk displayed excellent antimicrobial activity (reduction rate: similar to 38-55%) against the fungal strain Aspergillus niger. Lastly the study envisages developing a sustainable technology for utilization of bio-resources for the economic growth of the rural weaver's societies in India. (C) 2012 Elsevier Ltd. All rights reserved.