A Focused Library of NO‐Donor Compounds with Potent Antiproliferative Activity Based on Green Multicomponent Reactions

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.

Multicomponent Reaction-Assisted Drug Discovery: A Time- and Cost-Effective Green Approach Speeding Up Identification and Optimization of Anticancer Drugs

Multicomponent reactions (MCRs) have emerged as a powerful strategy in synthetic organic chemistry due to their widespread applications in drug discovery and development. MCRs are flexible transformations in which three or more substrates react to form structurally complex products with high atomic efficiency. They are being increasingly appreciated as a highly exploratory and evolutionary tool by the medicinal chemistry community, opening the door to more sustainable, cost-effective and rapid synthesis of biologically active molecules. In recent years, MCR-based synthetic strategies have found extensive application in the field of drug discovery, and several anticancer drugs have been synthesized through MCRs. In this review, we present an overview of representative and recent literature examples documenting different approaches and applications of MCRs in the development of new anticancer drugs.

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.

Tuning NO release of organelle-targeted furoxan derivatives and their cytotoxicity against lung cancer cells

We herein report a study on a set of hybrid compounds in which 3-R-substituted furoxan moieties (R = CH₃, CONH₂, CN, SO₂C₆H₅), endowed with varying NO-releasing capacities, are joined to a mitochondrial probe, rhodamine B. Each product has been investigated for its ability to release NO both in physiological solution, in the presence of cysteine, and in A549 lung adenocarcinoma cancer cells. The cytotoxicity of all the products against the aforementioned cancer cells has been assessed, including the structurally related compounds with no mitochondrial targeting, which were taken as a reference. In the case of the models bearing the -CH₃ and -CONH₂ groups at the 3-position on the furoxan, only the targeted models showed a significant cytotoxic activity, and only at the highest concentrations, in accordance with their weak NO-releasing properties. On the contrary, the presence of the strong electron-withdrawing groups, as -CN and -SO₂C₆H₅, at the 3-position gave rise to anticancer agents, likely because of the high NO-releasing and of their capability of inhibiting cellular proteins by covalent binding. In detail, the rhodamine hybrid containing the 3-SO₂C₆H₅ substituted furoxan moiety emerged as the most interesting product as it showed high cytotoxicity over the entire concentration range tested. This substructure was also linked to a phenothiazine scaffold that is able to accumulate in lysosomes. Nevertheless, mitochondrial targeting for these NO-donor furoxan substructures was found to be the most efficient.

de la Torre A, M. Muñiz F, Pertino MW, Alarcón B, Ormazabal V, Nova-Lamperti E, Zúñiga FA, Jiménez CA. Synthesis and Cytotoxic Analysis of Novel Myrtenyl Grafted Pseudo-Peptides Revealed Potential Candidates for Anticancer Therapy

Myrtenal is a natural monoterpene isolated from essential oils of several plants and their derivates have shown to have several biological properties including cytotoxicity. The cytotoxic activity of these derivates are being investigated for their antitumor effect leading to the development of potential anticancer agents. In this study, novels Myrtenyl grafted pseudo-peptides were designed, synthesized and functionally characterized as possible therapeutic agents for cancer treatment. Thirteen novel Myrtenyl grafted pseudo-peptides were prepared in high atom economy and efficiency by a classic Ugi-4CR and sequential post-modification. Their structures were confirmed by NMR, and ESI-MS, and its cytotoxic activity was evaluated in three cancer cell lines and primary CD4+ T cells at different proliferative cycles. Our results revealed that some of these compounds showed significant cytotoxicity against human gastric, breast and colon adenocarcinoma cells lines, but not against human dermal fibroblast cell line. Moreover, from the thirteen novel myrtenyl synthesized the compound (1R,5S)-N-{[1-(3-chlorophenyl)-1H-1,2,3-triazol-4-yl]methyl}-N-[2-(cyclohexylamino)-2–oxoethyl]-6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-carboxamide (3b) proved to be the best candidate in terms of acceptable EC₅₀, and E_max values in cancer cell lines and at inducing cytotoxicity in CD4+ T cells undergoing active proliferation, without affecting non-proliferating T cells. Overall, the synthesis and characterization of our Myrtenyl derivates revealed novel potential anticancer candidates with selective cytotoxic activity.