Novel ciprofloxacin hybrids using biology oriented drug synthesis (BIODS) approach: Anticancer activity, effects on cell cycle profile, caspase-3 mediated apoptosis, topoisomerase II inhibition, and antibacterial activity.

As we are interested in synthetizing biologically active leads with dual anticancer and antibacterial activity, we adopted biology oriented drug synthesis (BIODS) strategy to synthesize a series of novel ciprofloxacin (CP) hybrids. The National Cancer Institute (USA) selected seventeen newly synthesized compounds for anticancer evaluation against 59 different human tumor cell lines. Five compounds 3e, 3f, 3h, 3o and 3p were further studied through determination of IC50 values against the most sensitive cancer cell lines. In vitro results showed that the five compounds exhibited potent anticancer activity against test cell lines in nanomolar to micromolar range, with IC50 values between 0.72 and 4.92 μM, which was 9 to1.5 folds more potent than doxorubicin. In this study, two promising potent anticancer CP hybrids, 3f and 3o, were identified. The anti-proliferative activity of these compounds appears to correlate well with their ability to inhibit Topo II (IC50  = 0.58 and 0.86 μM). It is worth mentioning that compound 3f was 6 folds more potent than doxorubicin, 5 folds more potent than amsacrine and 1.5 folds more potent than etoposide. At the same time, compound 3o showed 4 folds more inhibitory activity against Topo II than doxorubicin, 3 folds more potent than amsacrine and almost equipotent activity to etoposide. Activation of damage response pathway of the DNA leads to cell cycle arrest at G2/M phase, accumulation of cells in pre-G1 phase and annexin-V and propidium iodide staining, indicating that cell death proceeds through an apoptotic mechanism. Moreover, compounds 3f and 3o showed potent pro-apoptotic effect through induction of the intrinsic mitochondrial pathway of apoptosis. This mechanistic pathway was confirmed by a significant increase in the level of active caspase-3 compared to control. This observation may indicate that both CP hybrids can chelate with zinc, a powerful inhibitor of procaspase-3 enzymatic activity, so procaspase-3 may process itself to the active form. The synthesized CP derivatives were tested for their in vitro antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa strains. The results proved that all of the test compounds have shown good to excellent antibacterial activity, as compared to its parent molecule ciprofloxacin. Compounds 2, 3b, 3k, 3l, 3m, 3p, 5a, 5b, 5d and 5e exhibited equipotent or comparable activity to ciprofloxacin against the test strains. Compounds 3p and 5a were more potent than ciprofloxacin against Pseudomonas aeruginosa, a common organism causing infections in granulocytopenic cancer patients.