-idin
noun suffix
or -idine: chemical compound related in origin or structure to another compound
    toluidine
    guanidine

-i·din
\ədə̇n, əd^ən\ noun suffix
or -i·dine \əˌdēn, ədə̇n, əd^ən\
(-s)
Etymology: International Scientific Vocabulary -ide (I) + -in, -ine
: chemical compound related in origin or structure to another compound: as
 a. usually -idin : aglycon of a glycoside
  < pelargonidin from pelargonin >
 b. usually -idine : completely hydrogenated form of a cyclic base
  < pyrrolidine from pyrrole >
  < thiazolidine from thiazole >
 c. usually -idine : base obtained otherwise than by hydrogenation
  < toluidine or tolidine from toluene >
  < guanidine from guanine >