Dye precursor from plants of the medicago genus, its preparation and its use in the manufacture of dyestuffs

摘要

Preparation of a composition containing a colourant precursor comprises macerating plants, parts of plants or in vitro cell cultures of the genus Medicago, separating and recovering an at least partially purified fraction which is free from components having a molecular weight of greater than 3500, this fraction being capable of reacting with 1,4-naphthoquinone in aqueous solution to give at least one coloured product.