In vitro screening of potential anti-cancer chemicals: effect of purine pyrimidine analogues on seed germination.

Germinating Cicer arietinum seeds were used to simulate embryonic tissue for evaluating toxicity of purine and pyrimidine analogues. 6-Mercaptopurine stimulated germination, whereas 8-azaadenine, 8-azaguanine, 2,6-diaminopurine, 6-amino, 2-hydroxypurine and 5-fluorouracil inhibited germination. 6-Methyluracil, 5-aminouracil and methylxanthines, viz. caffeine, theophylline, theobromine and uric acid exhibited little inhibitory effects. RNA synthesis ensued immediately after water imbibition and reached maximum at 12 h of germination. 2,6-Diaminopurine, 8-azaadenine, 8-azaguanine and 5-fluorouracil inhibited RNA synthesis. Cyclic-AMP, adenosine, indole-3-acetic acid (IAA) and folic acid partially reversed the inhibitory effects produced by purine pyrimidine analogues. Several hitherto untested pyrimidine analogues inhibited germination as well as RNA synthesis. Inhibition of Escherichia coli dihydrofolate reductase was used for purposes of comparison.