Effect of sydnone SYD-1 on certain functions of LPS-stimulated macrophages

Sydnone: Synthesis, Reactivity and Biological Activities

Sydnones are among the most well-known mesoionic compounds. Since their synthesis in 1935 by Earl and Mecknay, numerous researches have shown that the chemical behavior, physical and biological properties of sydnones make them the most useful compounds in organic chemistry. Sydnones undergo thermal 1,3-dipolar cycloaddition reaction with dipolarophiles (alkynes or alkenes) to give exclusively derivatives containing a pyrazole moiety exhibiting numerous applications, such as pharmaceuticals and agrochemicals. However, the sydnone cycloaddition reaction with alkynes requires harsh conditions, like high temperatures and long reaction times, giving poor regioselectivity to the resulting products. To overcome these constraints, new reactions named CuSAC (Copper- Catalyzed Sydnone-Alkyne Cycloaddition) and SPSAC (Strain-Promoted Sydnone- Alkyne Cycloaddition) have been developed, leading to pyrazoles with interesting constant kinetics.

Novel piperonal 1,3,4-thiadiazolium-2-phenylamines mesoionic derivatives: Synthesis, tyrosinase inhibition evaluation and HSA binding study

A novel series of piperonal mesoionic derivatives (PMI 1-6) was synthesized. Tyrosinase inhibition in the presence of PMI-1, -2, -3, -4, -5 and -6 as well as human serum albumin (HSA) binding studies with PMI-5 and PMI-6 were done by spectroscopic and theoretical methods. The mesoionic compound PMI-5 is the most promising tyrosinase inhibitor with a noncompetitive inhibitory mechanism and an IC₅₀=124μmolL^-1. In accordance with the kinetic profile, molecular docking results show that PMI-5 is able to interact favorably with the tyrosinase active site containing the substrate molecule, L-DOPA, interacting with Val-247, Phe-263 and Val-282 residues. The spectroscopic results for the interaction HSA:PMI-5 and HSA:PMI-6 indicated that these mesoionic compounds can associate with HSA in the ground state and energy transfer can occur with high probability. The binding was moderate, spontaneous and can perturb significantly the secondary structure of the albumin. The molecular docking results suggest that PMI-5 and PMI-6 are able to be accommodated inside the Sudlow's site I in HSA, interacting with hydrophobic and hydrophilic amino acid residues.

Sydnone 1: A Mesoionic Compound with Antitumoral and Haematological Effects In Vivo

This study evaluated the antitumour activity of the mesoionic compound sydnone 1 (Syd-1) against Walker-256 carcinosarcoma. Tumour cells were subcutaneously inoculated in the hind limb in male Wistar rats. The animals were orally treated for 12 days with Syd-1 (75 mg/kg) or vehicle. At the end of treatment, considerable decreases in tumour volume and tumour weight were observed in treated animals. Samples of these tumours presented increases in apoptotic bodies and pro-apoptotic protein expression (Bax and p53), while the expression of the anti-apoptotic protein Bcl-2 was reduced. A decrease in reduced glutathione levels and an increase in glutathione peroxidase activity were observed in tumour after Syd-1 treatment. However, significant splenomegaly was evident in animals that received Syd-1, most likely attributable to the induction of haemolysis. This study demonstrated the antitumour activity of Syd-1 against Walker-256 carcinosarcoma. Its mechanism of action is linked to the activation of apoptotic pathways that lead to tumour cell death.