Definition from Wiktionary, the free dictionary
From French xantheine, apparently arbitrary respelling to distinguish similarly spelled chemicals.
- (chemistry) The water-soluble part of the yellow carotenoid pigment present in the cell sap of some plants.
Usage notes 
- Xanthein and similar sounding words have also been used for several different yellow compounds derived from plants.
chemistry: the water-soluble part of the yellow carotenoid pigment present in the cell sap of some plants