Cleistanthus collinus, a toxic plant, contains three glycosidic compounds, Cleistanthin A, B and C. Cultured K562 cells were treated with 1μg/ml and 10μg/ ml of each Cleistanthins (A and B). At higher concentration a significant dose dependent decrease has been noted in the incorporation of thymidine and uridine into DNA and RNA, respectively. However, no significant difference in leucine incorporation into proteins was discerned. Hence present study shows Cleistanthin A and B inhibition nucleotides (DNA, RNA) with no difference in aminoacid transportation into macromolecules (Protein) into cell cytoplasm of K562 cells. However it dos not affect transport of nucleotides and aminoacids into the cytoplasm. Thus, these results showed that the cell growth/ proliferation is checked by these compounds at the replication and transcriptional level, but not at the translational level.