Mechanism of Thiol-Induced Nitrogen(II) Oxide Donation by Furoxans: a Quantum-Chemical Study

Furoxan-piplartine hybrids as effective NO donors and ROS inducers in PC3 cancer cells: design, synthesis, and biological evaluation

Conjugation of the naturally occurring product piplartine (PPT, 1), which is a potent cytotoxic compound and ROS inducer, with a diphenyl sulfonyl-substituted furoxan moiety (namely, 3,4-bis(phenylsulfonyl)-1,2,5-oxadiazole-2-oxide), an important type of NO donor, via an ether linker of different chain lengths is described, characterized and screened for the anticancer potential. The cytotoxicity of the new hybrids was evaluated on a panel of human cancer cell lines (MCF-7, PC3 and OVCAR-3) and two non-cancer human cells (MCF10A and PNT2). In general, the synthesized hybrids were more cytotoxic and selective compared to their furoxan precursors 4-6 and PPT in the above cancer cells. Particularly, PC3 cells are the most sensitive to hybrids 7 and 9 (IC50 values of 240 nM and 50 nM, respectively), while a lower potency was found for the prostate normal cells (IC50 = 17.8 μM and 14.1 μM, respectively), corresponding to selectivity indices of ca. 75 and 280, respectively. NO generation by the PPT-furoxan compounds in PC3 cells was confirmed using the Griess reaction. Furthermore, the cell growth inhibitory effect of 9 was significantly attenuated by the NO scavenger carboxy-PTIO. The intracellular ROS generation by 7 and 9 was also verified, and different assays showed that co-treatment with the antioxidant N-acetyl-l-cysteine (NAC) provided protection against PPT-induced ROS generation. Further mechanistic studies revealed that 7 and 9 had strong cytotoxicity to induce apoptosis in PC3 cells, being mediated, at least in part, by the NO-release and increase in ROS production. Notably, the ability of 9 to induce apoptosis was stronger than that of 7, which may be attributed to higher levels of NO released by 9. Compounds 7 and 9 modulated the expression profiles of critical regulators of cell cycle, such as CDKN1A (p21), c-MYC, and CCND1 (cyclin D1), as well as induced DNA damage. Overall, tethering the furoxan NO-releasing moiety to the cytotoxic natural product PPT had significant impact on the potential anticancer activity and selectivity of the novel hybrid drug candidates, especially 9, as a result of synergistic effects of both furoxan and PPT's ability to release NO, generate ROS, induce DNA damage, and trigger apoptosis.

Recent progress in synthesis and application of furoxan

This review highlights recent developments in the synthesis and application of furoxan. The chemistry of furoxan is relatively underdeveloped compared to that of other heterocycles owing to its difficult synthesis, which is ascribed to the labile nature of this molecule under various reaction conditions. Nevertheless, recent studies have conducted a variety of bond-forming reactions on the furoxan ring via a post-ring introduction of substituents (PRIS) strategy. This strategy enables the synthesis of furoxan molecules of interest more directly than the conventional methods that rely on the pre-installation of substituents on the furoxan ring precursors. In this review, the PRIS strategy for furoxan synthesis is classified and discussed according to the type of bond formed. Additionally, recent progress in the application of furoxan molecules, predominantly facilitated by the development of new synthetic methods, is covered in this review.

New Nitric Oxide-Releasing Compounds as Promising Anti-Bladder Cancer Drugs

Bladder cancer is a worldwide problem and improved therapies are urgently needed. In the search for newer strong antitumor compounds, herein, we present the study of three nitric oxide-releasing compounds and evaluate them as possible therapies for this malignancy. Bladder cancer cell lines T24 and 253J were used to evaluate the antiproliferative, antimigratory, and genotoxic effects of compounds. Moreover, we determined the NF-κB pathway inhibition, and finally, the survivin downregulation exerted by our molecules. The results revealed that compounds 1 and 3 exerted a high antiproliferative activity against bladder cancer cells through DNA damage and survivin downregulation. In addition, compound 3 reduced bladder cancer cell migration. We found that nitric oxide donors are promising molecules for the development of a new therapeutic targeting the underlying mechanisms of tumorigenesis and progression of bladder cancer.

Water-Soluble Salts Based on Benzofuroxan Derivatives-Synthesis and Biological Activity

A series of novel water-soluble salts of benzofuroxans was achieved via aromatic nucleophilic substitution reaction of 4,6-dichloro-5-nitrobenzofuroxan with various amines. The salts obtained showed good effectiveness of the pre-sowing treatment of seeds of agricultural crops at concentrations of 20-40 mmol. In some cases, the seed treatment with salts leads not only to improved seed germination, but also to the suppression of microflora growth. Additionally, their anti-cancer activityin vitrohas been researched. The compounds with morpholine fragments or a fragment of N-dimethylpropylamine, demonstrated the highest cytotoxic activity, which is in good correlation with the ability to inhibit the glycolysis process in tumor cells. Two compounds 4e and 4g were selected for further experiments using laboratory animals. It was found that the lethal dose of 50% (LD50) is 22.0 ± 1.33 mg/kg for 4e and 13.75 ± 1.73 mg/kg for 4g, i.e., compound 4e is two times less toxic than 4g, according to the mouse model in vivo. It was shown that the studied compounds exhibit antileukemia activity after a single intraperitoneal injection at doses from 1.25 to 5 mg/kg, as a result of which the average lifespan of animals with a P388 murine leukemia tumor increases from 20 to 28%. Thus, the water-soluble salts of benzofuroxans can be considered as promisingcandidates for further development, both as anti-cancer agents and as stimulants for seed germination and regulators of microflora crop growth.

Greener Synthesis of Antiproliferative Furoxans via Multicomponent Reactions

Prostate and bladder cancers are commonly diagnosed malignancies in men. Several nitric oxide donor compounds with strong antitumor activity have been reported. Thus, continuing with our efforts to explore the chemical space around bioactive furoxan moiety, multicomponent reactions were employed for the rapid generation of molecular diversity and complexity. We herein report the use of Ugi and Groebke-Blackburn-Bienaymé multicomponent reactions under efficient, safe, and environmentally friendly conditions to synthesize a small collection of nitric-oxide-releasing molecules. The in vitro antiproliferative activity of the synthesized compounds was measured against two different human cancer cell lines, LNCaP (prostate) and T24 (bladder). Almost all compounds displayed antiproliferative activity against both cancer cell lines, providing lead compounds with nanomolar GI50 values against the cancer bladder cell line with selectivity indices higher than 10.

Mechanisms of nitric oxide generation in living systems

In modern chemical and biochemical studies, special attention is paid to molecular systems capable of generating nitric oxide (NO), which is one of the most important signalling molecules in the body and can trigger a whole cascade of reactions. Despite the importance of this molecule, the mechanisms of its formation in living organisms remain a subject of debate. This review combines the most important methods of releasing NO from endogenous and exogenous sources. The history of endogenous NO donors dates back more than 150 years, since the synthesis of nitroglycerin, which remains the standard vasodilator today, even though it is known that it and many other similar compounds lead to the development of a nitrate tolerance. Particular awareness is devoted to the mechanisms of NO formation without the participation of enzymes, since these methods are most important for creating exogenous sources of NO as drugs. The study of NO formation methods is centred on both the creation of new NO donors and understanding the mechanisms of tolerance to them.

Selective Methylmagnesium Chloride Mediated Acetylations of Isosorbide: A Route to Powerful Nitric Oxide Donor Furoxans

Isosorbide was functionalized with furoxan for the first time to give adducts that release nitric oxide up to 7.5 times faster than the commercial vasodilator, isosorbide-5-mononitrate (Is5N). The synthesis was facilitated by MeMgCl-mediated selective acetylation of isosorbide or selective deacetylation of isosorbide-2,5-diacetate, which was rationalized in terms of a more stable 5-alkoxide magnesium salt using DFT. Isosorbide-furoxans are safer to handle than Is5N due to greater thermal stability.