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Discovery of isatin-indolo[2,3- b ]quinoxaline hybrids as templates for new DNA intercalators and overcoming platinum-based resistance in ovarian cancer. [Display omitted] • Synthesized and evaluated isatin-indoloquinoxaline hybrids against ovarian cancer cells, including sensitive and drug-resistant types. • Most active compound showed better anti-proliferative activity than reference drugs, overcoming platinum-based resistance. • Mechanistic insights revealed comparable inhibition of topoisomerase II and DNA binding affinity to doxorubicin. • In silico studies indicated favorable physicochemical, pharmacokinetics, and toxicity parameters for the compounds. Herein, a series of isatin tethered indolo[2,3- b ]quinoxaline hybrids was synthesized by considering the pharmacophoric features of known DNA intercalators and topoisomerase II inhibitors. The anti-proliferative properties of the synthesized compounds were evaluated against ovarian cancer cell lines (SKOV-3 and Hey A8). Four of the compounds exhibited promising anti-proliferative activities, with one of them being 10-fold more potent than cisplatin against drug-resistant Hey A8 cells. Further investigations were carried out to determine the DNA intercalating affinities of the most active compounds as potential mechanisms for their anti-proliferative activities. ADMET in silico studies were performed to assess the physicochemical, pharmacokinetics, and toxicity parameters of active compounds. This study, to the best of our knowledge, is the first report on the potential of isatin-indoloquinoxaline hybrids as structural blueprints for the development of new DNA intercalators. Additionally, it explores their potential to circumvent platinum-based resistance in ovarian cancer. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study is to synthesize indolo[2,3- b ]quinoxaline-4-aminoquinoline-based hybrids and evaluate their effectiveness against chloroquine-susceptible (3D7) and resistant (W2) Plasmodium falciparum strains, with expected inhibition of P. falciparum chloroquine resistance transporter ( Pf CRT) and heme. Methods: The hybrids were synthesized and in vitro evaluated against both susceptible and resistant strains. Molecular docking and studies were conducted to assess the binding affinities for the Pf CRT protein. Additionally, heme-inhibition studies using hemin chloride provided valuable insights into the interaction between the ligand and heme. The binding constant (logK) was calculated, providing quantitative details about the strength of this interaction. Conclusion: The synthesized hybrids showed reasonable potency against both P. falciparum strains. The most potent hybrid 10d , with fluorine-substitution exhibited good activity. Molecular docking studies indicated strong binding affinities for the Pf CRT protein. Heme inhibition studies further supported the potential of 10d as an effective anti-plasmodial agent.

Abstract: Synthesis of 2,3-disubstituted 1-alkylpyrrolo[2,3-b]quinoxalines was accomplished through the reaction of 3-chloroquinoxalin-2-amines with internal alkynes in the presence of Pd(OAc)2, NaOAc, and KOtBu in DMSO. This method afforded desired pyrrolo[2,3-b]quinoxalines in 65-92% reaction yields. The minimum inhibition concentration and minimum bactericidal concentration determinations against Micrococcus luteus and Pseudomonas aeruginosa revealed that some of the synthesized compounds showed the same values compared to tetracycline. These compounds could be used in the future research for the development of new antibiotics.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: 6H-Indolo[2,3-b]quinoxaline was studied as a covalently bound heteroaromatic intercalator. Six monomers were synthesized and incorporated into DNA oligonucleotides. Through a study of linker length dependence it was concluded that the linker between the oligo and the intercalator must consist of at least five C atoms in order to stabilize a DNA duplex. An intercalator with a 2′-deoxy-d-riboside linker to the oligo could also stabilize a DNA/RNA duplex, while (S)-4-(6-methylindolo[2,3-b]quinoxalin-3-ylmethoxy)-butane-1,2-diol was able to stabilize both DNA/DNA, DNA/RNA and a DNA/LNA duplex. Mismatch studies revealed a huge sensitivity to the C–C mismatch at the 5′-site of the intercalator. [Copyright &y& Elsevier]

Abstract: The synthesis is described of a bis-ene-1,2-dithiolate pro-ligand, designed to model the stereochemical situation in the cofactor of the tungsten enzyme ferredoxin aldehyde oxidoreductase from Pyrococcus furiosus. Each masked ene-1,2-dithiolate unit is mounted on a pyrano[2,3-b]tetrahydroquinoxaline tricycle, comparable to the pyrano[2,3-g]tetrahydropteridines found in all molybdoenzymes and tungsten analogues. Hydrolytic release of the bis-ligand was confirmed by its entrapment as a double (η5-C5H5)Co complex. [Copyright &y& Elsevier]

Abstract: Reduction of indolo[2,3-b]quinoxalines with zinc in the presence of an anhydride gave N,N-diacyl trapped 6,11-dihydroindolo[2,3-b]quinoxalines in 43–92% yields. When the reduction with zinc was performed in TFA/TFAA, an unexpected ring opened product was isolated in 49% yield. The structure of this product could be identified as 1,2-dihydro-1-trifluoroacetyl-3-[(2-trifluoroacetylamino)phenyl]quinoxaline. [Copyright &y& Elsevier]

Background: This paper showed the synthetic capability of the indolo[2,3-b]quinoxaline nucleus to be provided as an excellent precursor for the synthesis of various heterocyclic compounds. These synthetic routes proceed via the formation of 3-(6H-indolo[2,3-b]quinoxalin-6-yl) propane hydrazide (2). The carbohydrazide 2 and its reactions with different reagents give five and six-membered rings, such as 1,3,4-thiadiazole, 1,3,4- oxadiazole, 1,2,4-triazole, and 1,2,4-triazine., Methods: All chemicals used in the current study were of analytical grade. Melting points were determined using an APP Digital ST 15 melting point apparatus and were uncorrected. FT-IR spectra were recorded on a Pye- Unicam SP3-100 and Shimadzu-408 spectrophotometers in KBr pellets and given in (cm -1 ) KBr. The NMR spectra were detected by a Bruker AV-400 spectrometer (400 MHz for 1 H, 100 MHz for 1 C and 40.55 MHz for 15 N), Institute of Organic Chemistry, Karlsruhe, Germany. Chemical shifts were expressed as δ (ppm) with TMS as an internal reference. Mass spectrometry was provided on a Varian MAT 312 instrument in EI mode (70 eV)., Results: The target compounds were obtained, and their structures were completely elucidated by various spectral and elemental analyses (Ft-IR, 1 H-NMR, 13 ;C-NMR, and mass spectrometry)., Conclusion: The current work showed a view of the reactivity of the carbohydrazide group. The carbohydrazide 2 was obtained from the hydrazinolysis of carboethoxy compound 1 and exploited as a key intermediate to synthesize heterocyclic compounds with different rings., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)