Noncytotoxic Pyrrolobenzodiazepine-Ciprofloxacin Conjugate with Activity against Mycobacterium tuberculosis

N-Acylated Ciprofloxacin Derivatives: Synthesis and In Vitro Biological Evaluation as Antibacterial and Anticancer Agents

A novel series of N-acylated ciprofloxacin (CP) conjugates 1-21 were synthesized and screened as potential antimicrobial agents. Conjugates 1 and 2 were 1.25-10-fold more potent than CP toward all Staphylococci (minimal inhibitory concentration 0.05-0.4 μg/mL). Most of the chloro- (3-7), bromo- (8-11), and CF₃-alkanoyl (14-16) derivatives expressed higher or comparable activity to CP against selected Gram-positive strains. A few CP analogues (5, 10, and 11) were also more effective toward the chosen clinical Gram-negative rods. Conjugates 5, 10, and 11 considerably influenced the phases of the bacterial growth cycle over 18 h. Additionally, compounds 2, 4-7, 9-12, and 21 exerted stronger tuberculostatic action against three Mycobacterium tuberculosis isolates than the first-line antitubercular drugs. Amides 1, 2, 5, 6, 10, and 11 targeted gyrase and topoisomerase IV at 2.7-10.0 μg/mL, which suggests a mechanism of antibacterial action related to CP. These findings were confirmed by molecular docking studies. In addition, compounds 3 and 15 showed high antiproliferative activities against prostate PC3 cells (IC₅₀ 2.02-4.8 μM), up to 6.5-2.75 stronger than cisplatin. They almost completely reduced the growth and proliferation rates in these cells, without a cytotoxic action against normal HaCaT cell lines. Furthermore, derivatives 3 and 21 induced apoptosis/necrosis in PC3 cells, probably by increasing the intracellular ROS amount, as well as they diminished the IL-6 level in tumor cells.

Covalent DNA Binding Is Essential for Gram-Negative Antibacterial Activity of Broad Spectrum Pyrrolobenzodiazepines

It is urgent to find new antibiotic classes against multidrug-resistant bacteria as the rate of discovery of new classes of antibiotics has been very slow in the last 50 years. Recently, pyrrolobenzodiazepines (PBDs) with a C8-linked aliphatic-heterocycle have been identified as a new broad-spectrum antibiotic class with activity against Gram-negative bacteria. The active imine moiety of the reported lead pyrrolobenzodiazepine compounds was replaced with amide to obtain the non-DNA binding and noncytotoxic dilactam analogues to understand the structure-activity relationship further and improve the safety potential of this class. The synthesised compounds were tested against panels of multidrug-resistant Gram-positive and Gram-negative bacteria, including WHO priority pathogens. Minimum inhibitory concentrations for the dilactam analogues ranged from 4 to 32 mg/L for MDR Gram-positive bacteria, compared to 0.03 to 2 mg/L for the corresponding imine analogues. At the same time, they were found to be inactive against MDR Gram-negative bacteria, with a MIC > 32 mg/L, compared to a MIC of 0.5 to 32 mg/L for imine analogues. A molecular modelling study suggests that the lack of imine functionality also affects the interaction of PBDs with DNA gyrase. This study suggests that the presence of N10-C11 imine moiety is crucial for the broad-spectrum activity of pyrrolobenzodiazepines.

Bio-oriented synthesis of new sulphadiazine derivatives for urease inhibition and their pharmacokinetic analysis

Current research is based on biology-oriented synthesis of sulphadiazine derivatives and determination of their urease inhibitory activity. In this regard, a series of (E)-4-(benzylideneamino)-N-(pyrimidin-2-yl)benzenesulfonamide was synthesized from sulphadiazine and substituted aromatic aldehydes. The structures of synthesized compounds were ascertained by spectroscopic techniques, such as, FTIR, NMR and HRMS analysis, and in-vitro and in-silico investigation were carried out for the inhibition of urease. Ureases are harmful for humans by producing by-products of urea (ammonia and carbon dioxide). The most active compound (3l) against urease exhibited IC50 value of 2.21 ± 0.45 µM which is 10 times more potent than the standard thiourea (20.03 ± 2.06 µM). It is noteworthy that most of our synthesized compounds showed significant to excellent activities against urease enzyme and most of them substituted by halogen or hydroxy groups at ortho and para positions in their structures. Inhibition of enzyme by the synthesized analogues was in descending order as 3l > 3a > 3b > 3q > 3e > 3o > 3s > 3t > 3g > 3k > 3r > 3f > 3m > 3p > 3n > 3j > 3i > 3h. Moreover, molecular docking studies were performed to rationalize the binding interactions of the synthesized motifs with the active pocket of the urease enzyme. The synthesized sulphadiazine derivatives (3a-u) were found to be non-toxic, and presented passive gastrointestinal absorption.

Synthesis and Biological Evaluation of a Novel C8-Pyrrolobenzodiazepine (PBD) Adenosine Conjugate. A Study on the Role of the PBD Ring in the Biological Activity of PBD-Conjugates

Here we sought to evaluate the contribution of the PBD unit to the biological activity of PBD-conjugates and, to this end, an adenosine nucleoside was attached to the PBD A-ring C8 position. A convergent approach was successfully adopted for the synthesis of a novel C8-linked pyrrolo(2,1-c)(1,4)benzodiazepine(PBD)-adenosine(ADN) hybrid. The PBD and adenosine (ADN) moieties were synthesized separately and then linked through a pentynyl linker. To our knowledge, this is the first report of a PBD connected to a nucleoside. Surprisingly, the compound showed no cytotoxicity against murine cells and was inactive against Mycobacterium aurum and M. bovis strains and did not bind to guanine-containing DNA sequences, as shown by DNase I footprinting experiments. Molecular dynamics simulations revealed that the PBD-ADN conjugate was poorly accommodated in the DNA minor groove of two DNA sequences containing the AGA-PBD binding motif, with the adenosine moiety of the ligand preventing the covalent binding of the PBD unit to the guanine amino group of the DNA duplex. These interesting findings shed further light on the ability of the substituents attached at the C8 position of PBDs to affect and modulate the biological and biophysical properties of PBD hybrids.