Of the 92 natural dyes listed in Colour Index, chemical structure of 67 dyes is disclosed. Many dyes have more than
one compound and some dyes have identical structures[26]. About more than 100 vegetable origin dyes, colouring
matter derived from root, leaf, bark, trunk or fruit of plants, list of the important sources are given in Table-2.
Extraction of plant natural colourants
Natural Dyes cannot be used directly from their renewable sources. Using raw materials for dyeing has many
limitations. Safe and cheap extraction of main colouring component is most important without affecting the
extraction conditions and avoiding any contamination in various extraction techniques. Several extraction
methodologies for natural dye that comply with both consumer preference and regulatory control and that are cost effective are becoming more popular. Some of the techniques of extractions of natural dyes [76] are
· Simple Aqueous Methods · Supercritical Fluid Extraction
· Complicated Solvent Systems · Ultrasonic Extraction