neopterins triol neopterin chebi_ontology neopterine 2-amino-6-(1,2,3-trihydroxypropyl)-4(3H)-pteridinone CHEBI:44294 CHEBI:28670 CHEBI:7511 1-(2-amino-4-hydroxy-6-pteridinyl)-1,2,3-propanetriol CHEBI:25499 6-(1',2',3'-trihydroxy)pterin primary amino compound