All
 D03 Heterocyclic Compounds D006571 +
 D03.438 Heterocyclic Compounds, 2-Ring D006574 +
 D03.438.759 Purines D011687 +
 D03.438.759.138 Adenine D000225 +
 D03.438.759.160 Allopurinol D000493 
 D03.438.759.758 Purinones D011688 +
 D03.438.759.794 Saxitoxin D012530 
 D03.438.759.854 Thioguanine D013866 
 D03.438.759.950 Zeatin D015026 
 D03.438.759.534 6-Mercaptopurine D015122