The growing demand for more natural products and the
toxicity problem in relation to synthetic dyes [1] are the
principal factors in encouraging a revival in the use of
natural dyes. Natural dyes can exhibit better biodegradability
and generally have a higher compatibility with the environment.
Recently, the potentiality of using natural dyes in
textile coloration as anti-UV and anti-microbial has been
investigated [2-4]. Several studies on the application of
natural dyes have been reported [5-10]. A review on the use
of natural dyes in textile coloration has been published [11].
Curcumin and madder are the most popular yellow and
red natural dyes, respectively. Curcumin is an active
ingredient in turmeric (Curcuma longa L) which is widely
used as a food colorant. It is called C.I. Natural Yellow 3;
WHO (World Health Organization) and FAO (Food and
Agriculture Organization) committees have approved it as a
food additive [12]. Curcumin exists in a keto-enol tautomerism
with equilibrium strongly favoring an enol form (Figure 1).
The enol structure enables curcumin to form additional interand
intramolecular hydrogen bonds [13-15].
Madder, the root of Rubia tinctorum L., has a long tradition
as a dyestuff because of its bright red color. It has been
cultivated as a source of dyestuff since antiquity in central