A series of novel compounds carrying pyrazino[1,2-a]indol-1(2H)-one scaffold (5a-g) and their reaction
intermediates, indole-2-carboxamides, (3a-g) were synthesized and evaluated for their ability to
inhibit reactive oxygen species (ROS) generation, antioxidant activity and anticancer activity against a
panel of cancer cell lines using MTT assay. The results showed that these compounds can inhibit ROS
generation during the metabolic phase of phagocytosis in a dose-dependent manner where compounds
5d and 5e were the most potent samples with higher inhibitory activities (IC50 values 3.3 and
1.4 mM, respectively) than that of the reference acetylsalicylic acid (IC50 ¼ 9.7 mM). Results for the
determination of potential antioxidant properties of the synthesized compounds showed that compounds
5d and 5e containing pyrazino[1,2-a]indol-1-one backbone were the most acive and even
comparable to Trolox. Compounds 3d-f and 5d-f with the least IC50 values in MTT assay were tested
against three known anticancer targets EGFR, BRAF and Tubulin. Histopathological and immunohistochemical
study were performed to determine the consequence of exposure to chronic low dose of
chlorpyrifos on the testis of male mice and results revealed that these effects can be ameliorated by cotreatment
with the most active antioxidant compounds 5d and 5e. Finally, molecular docking studies
were performed to explore the binding mode of the most active compounds against EGFR and BRAF
kinases.