Synthesis, structural characterization and antibacterial studies of trisubstituted guanidines and their copper(II) complexes

New ferrocene integrated amphiphilic guanidines: Synthesis, spectroscopic elucidation, DFT calculation and in vitro α-amylase and α-glucosidase inhibition combined with molecular docking approach

Three N, N', N″-trisubstituted ferrocenyl guanidines (MG-10, MG-12 and MG-14) were synthesized, characterized by several analytical methods such as FT-IR, ¹H and ¹³C NMR, elemental analysis and UV-visible spectroscopy. These compounds have long chain aliphatic groups therefore their aliphatic nature has been evaluated by determining their critical micelle concentration (CMC). CMC point decreases from 0.036 mM to 0.013 mM with increase in the aliphatic chain length. The quantum mechanical parameters such as the energy of frontier molecular orbitals (E_HOMO and E_LUMO) and the Mulliken charge distribution on the optimized structures were determined using a DFT/B3LYP method combined with the 6-31G (d,p) basis set in the gas phase. The in vitro antidiabetic activity of synthesized compounds showed that MG-12 has IC₅₀value 23.10 μg/mL against α-amylase while MG-10 has IC₅₀value 27.32 μg/mL against α-glucosidase with the respective standard Acarbose (IC₅₀value 20.12 μg/mL). Theoretical docking analysis demonstrated that MG-10 and MG-12 interacted with α-amylase by 3 types of interaction, including hydrogen bonds, hydrophobic interactions and electrostatic interactions.

Novel Polyhydroquinoline-Hydrazide-Linked Schiff's Base Derivatives: Multistep Synthesis, Antimicrobial, and Calcium-Channel-Blocking Activities

Polyhydroquinoline (PHQ) are the unsymmetrical Hantzsch derivatives of 1,4-dihydropyridines with several biological applications. In this work, twenty-five (3-27) new Schiff's base derivatives of polyhydroquinoline hydrazide were synthesized in excellent to good yields by a multi-component reaction. The structures of the synthesized products (1-27) were deduced with the help of spectroscopic techniques, such as 1H-, 13C -NMR, and HR-ESI-MS. The synthesized products (1-27) were tested for their antibacterial and in vitro calcium -channel-blocking (CCB) potentials using the agar-well diffusion method, and isolated rat aortic ring preparations, respectively. Among the series, sixteen compounds were found to inhibit the growth of Escherichia coli and Enterococcus faecalis. Among them, compound 17 was observed to be the most potent one at a dose 2 µg/mL, with an 18 mm zone of inhibition against both bacteria when it was compared with the standard drug amoxicillin. Eight compounds showed CCB activity of variable potency; in particular, compound 27 was more potent, with an EC50 value of 0.7 (0.3-1.1) µg/mL, indicating their CCB effect.

Synthesis and crystal structure analyses of tri-substituted guanidine-based copper(II) complexes

Three guanidine-derived tri-substituted ligands viz. N-pivaloyl-N′,N″-bis-(2-methoxyphenyl)guanidine (L1), N-pivaloyl-N′-(2-methoxyphenyl)-N″-phenylguanidine (L2) and N-pivaloyl-N′-(2-methoxyphenyl)-N″-(2-tolyl)guanidine (L3) were reacted with Cu(II) acetate to produce the corresponding complexes. The significance of the substituent on N″ for the resulting molecular structures and their packing in the solid state has been studied with respect to the structural specifics of the corresponding Cu(II) complexes. The key characteristic of the guanidine-based metal complexation with Cu(II) is the formation of an essentially square planar core with an N2O2 donor set. As an exception, in the complex of L1, the substituent’s methoxy moiety also interacts with the Cu(II) center to generate a square-pyramidal geometry. The hydroxyl groups of the imidic acid tautomeric forms of L1–L3, in addition to N″, are also bonded to Cu(II) in all three complexes rather than the nitrogen donor of the guanidine motif.