pter·i·dine 
(tĕrĭ-dēn′)
(tĕrĭ-dēn′)n.
1. A yellow crystalline compound, C6H4N2, having two fused six-member aromatic rings each containing two nitrogen atoms and four carbon atoms. One of the rings is a pyrimidine; the other is a pyrazine.
2. Any of a group of organic compounds derived from this compound, including folic acid and the pigments of butterfly wings.
[German Pteridin : Pter(in), pigment of insect wings (from Greek pteron, wing; see -PTER) + -id, -ide + -in, -ine.]