Extraction and characterization of natural dyes from euclea divinorum and erythrina abyssinica for textile dyeing

Abstract

Most of the dyes used in the textile industry are synthetic but recently the use of natural dyes has regained interest due to health hazards associated with synthetic dyes. Synthetic dyes are non-biodegradable, carcinogenic, allergic to the skin and toxic to the environment, therefore there is need to explore natural dyes to satisfy the increasing demand for environmental friendly dyes. Euclea divinorum and Erythrina abyssinica plants have been used traditionally by Kenyan communities as a dye but their potential as a dye for textile dyeing has not been exploited. The aim of this study was to extract dyes from the root bark of E. divinorum and stem bark of E. abyssinica for textile dyeing. The specific objectives were to: extract and characterize the natural dye from E. divinorum and E. abyssinica plants; optimize extraction and dyeing conditions of the dye extracts; compare the use of bio-mordants and synthetic (metal) mordants with the natural dye extracts on cotton fabric and determine the antioxidants and antimicrobial textile finishing properties of the dyes. Natural dye extraction was done using maceration method and characterized using Fourier transform Infra- Red spectroscopy (FTIR), Gas Chromatography Mass Spectroscopy (GC-MS) and Nuclear Magnetic Resonance (NMR). Optimization of extraction and dyeing conditions was conducted using Response Surface Methodology (RSM). The independent variables were time, temperature and M:L for extraction and pH, time and temperature for dyeing and the dependent variables were absorbance and color strength (K/S) for extraction and dyeing, respectively. Dyeing with metallic (alum, ferrous and tin) and bio-mordants (rosemary and mango extracts) was executed using pre-, post- and meta-mordanting methods. Dyeing characteristics were evaluated using color fastness and color strength. Antioxidant properties of the dye on fabric was determined using 2,2 -diphenyl-1-picrylhydrazyl radical (DPPH) method. Antimicrobial assays of dyed fabric against Escherichia coli and Staphylococcus aureus strains of bacteria were done using absorbance method. FTIR analysis indicated presence of O-H (at 3297 and 3647 cm -1 ), C-O (at 1373 and 1043 cm -1 ) and aromatic C=C (at 1618 and 1507 cm -1 ) functional groups for E. divinorum and E. abyssinica, respectively. GC-MS analysis of E. divinorum revealed that the major phytochemicals in the dye were lupeol and betulin. The NMR confirmed that the two isolated compounds were lupeol and betulin. The optimum extraction conditions for E. divinorum were M:L 7.5g:100mL, 84C and 146 minutes and M:L 10.6g:100mL, 77.2C and 131.0 minutes for E. abyssinica. The optimum dyeing conditions for E. divinorum were pH of 3.3, 82C and 68 minutes and pH of 5.0, 69.7C and 74.5 minutes for E. abyssinica. E. divinorum showed an excellent color fastness of 5 compared to E. abyssinica which was fairly good (3). The bio-mordants led to different shades of color as was achieved with metallic mordants. Rosemary improved the color strength from 0.612 to 0.911 almost similar to that of alum (0.954) for E. divinorum. An antioxidant activity of 72.5% and 63.1% for E. divinorum and E. abyssinica, respectively, was obtained and antimicrobial activity of 61.54% and 65.55 % against E. coli and S. aureus strains of bacteria, respectively, was observed. In conclusion the excellent color fastness of 5 of E. divinorum dye makes it a suitable alternative source of brown dye for dyeing cotton. This study established an important basis of bio-mordants applicable when dyeing cotton fabric with the studied natural dyes as suitable alternatives for metallic mordants. The good antioxidant and antimicrobial activity, indicates that the dyes are promising agents for future development of bioactive and protective textile. In order to maximize extraction and dyeing cotton with these natural dyes it is recommended that the optimum conditions be adopted. Mordanting process is also essential in achieving the best color fastness properties and different shades of brown and yellow for E. divinorum and E. abyssinica, respectively.