Most of them are synthetic in nature, made up of two key components: the chromophore, responsible for the color, and the
auxochrome, that not only supplement the chromophore but also render the solubility of molecule in water and give enhanced affinity to attach the fiber [2].
Flavonoids is a crystalline solid, a few (such as flavone glycosides) amorphous powder, color of flavonoids and molecular whether there cross conjugated system and
auxochrome group (- Oh, - OC[H.sub.3]) category, number and position of substitution on.
Generally, there are two important components in the dye molecules: chromophore component that is responsible for producing the color and the
auxochrome component which increases the affinity of the dye towards cellulose fibers [14, 43].
It contains azo (-N=N-) group as chromophore and sulfonate (- SO3H) group as
auxochrome. The color of Direct Red-28 dye alters in acidic and basic pH conditions from blue (at pH 2.0 -4.0) to red (at pH 12.0).