Antimicrobial activity of wool yarn dyed with Rheum emodi L. (Indian Rhubarb)

This work is an attempt to examine the effect of Rheum emodi L. as dye and its dyed wool yarns against two bacterial (Escherichia coli and Staphylococcus aureus) and two fungal (Candida albicans and Candida tropicalis) species. The dyeing was carried out using 5% and 10% o.w.f. dye concentration in presence and absence of ferrous sulphate, stannous chloride and alum mordants. The colour strength, CIELab values and fastness properties of dyed samples were also assessed. FTIR spectra of untreated, mordanted and dyed wool yarn were investigated to study the interaction between fibre, mordant and dye. The structural morphology of wool yarn was investigated by Scanning Electron Microscopy (SEM). The susceptibility tests for R. emodi L. were carried out in terms of disc diffusion, growth curve and viability assays against all the tested microorganisms. Dyed samples showed very effective antimicrobial properties showing more than 90% microbial reduction in both bacterial as well as fungal population.

► Beautiful light yellowish green shades were produced on wool yarns with Rheum emodi L. extract.
► R. emodi L. extract proved very effective in producing colour as well as antimicrobial effect on wool yarns.
► Wool-mordant-dye interaction pattern is also reported.
► Effect of mordants and dyes on surface morphology of yarn is illustrated using SEM photographs.