The Concentration Factor Effect Study of Etoposide Drug and Annona squamosa L. Seeds Extracts on Topoisomerase II Inhibition Model: Catalytic Inhibitory and Interfacial Poisons

Background: Topoisomerase II plays an important role in cell proliferation and DNA regulation. It isresponsible for loosening the supercoiled form of DNA and for condensing chromosomes in eukaryotic cells.Custard apple (Annona squamosa L.) (Annonaceae) has been one of the main ingredients of ethnomedicalpreparation for the treatment of tumors in some countries, and has cytotoxic effects on cancerous cell lines.Aim: assessment of Qualitative Inhibition (Catalytic Inhibitor or Interfacial Poisons) and Quantitative(IC50%) of Custard apple Plant Seeds; Crude Extract (CCE) and Alkaloid Extract (CAE) of HumanToposomerase IIA (TOP2A) compared to etoposide (VP-16) as a controlled drug. Methods: TOP2A (0.5unit) and pHOT1 DNA plasmid (62.5ng), DNA plasmid relaxation assay required for inhibition testing.Inhibitors, the seeds plant was extracted by 100% methanol for the preparation of crude with concentrations(240, 160, 100, 80, 40, 20, and 10 µg/ml) and alkaloid (100, 80, 60, 40, 20, 10 and 5 µg/ml), and the VP-16as a positive control drug (150, 100, 50, 25, 12.5, and 3.125 µg/ml). Results and Discussion: The CAEshowed a higher DNA plasmid relaxation inhibition, IC50% (27.46). The higher concentrations of CCEand CAE play as a Catalytic Inhibitory Compounds CICs (as suppressor compound) rather than InterfacialPoisons IFPs (as poisons compounds), quite the opposite at low concentrations. Higher concentrations mayinhibit the formation of the enzyme-DNA complex, resulting in the accumulation of the supercoiled formof the DNA plasmid due to inactivation of the enzyme function. In comparison, at low concentrations ofinhibiting factors the linear structure is accumulated, which means that both strands cannot be rejoined.Conclusions: The CAE had the highest inhibition activity on the TOPO2A compared to the other agents. Incontrast to the VP-16 drug, the CAE and CCE concentrations of this plant affected inhibition models.