Evaluation of Anticancer Activity of Nucleoside-Nitric Oxide Photo-Donor Hybrids

Herein, we report the synthesis of a new hybrid compound based on a 2'-deoxyuridine nucleoside conjugated with a NO photo-donor moiety (dU-t-NO) via CuAAC click chemistry. Hybrid dU-t-NO, as well as two previously reported 2'-deoxyadenosine based hybrids (dAdo-S-NO and dAdo-t-NO), were evaluated for their cytotoxic and cytostatic activities in selected cancer cell lines. dAdo-S-NO and dAdo-t-NO hybrids displayed higher activity with respect to dU-t-NO. All hybrids showed effective release of NO in the micromolar range. The photochemical behavior of the newly reported hybrid, dU-t-NO, was studied in the RKO colon carcinoma cell line, whereas the dAdo-t-NO hybrid was tested in both colon carcinoma RKO and hepatocarcinoma Hep 3B2.1-7 cell lines to evaluate the potential effect of NO released upon irradiation on cell viability. A customized irradiation apparatus for in vitro experiments was also designed.

Synthesis, Characterization, and Potential Usefulness in Liver Function Assessment of Novel Bile Acid Derivatives with Near-Infrared Fluorescence (NIRBAD)

Conventional serum markers often fail to accurately detect cholestasis accompanying many liver diseases. Although elevation in serum bile acid (BA) levels sensitively reflects impaired hepatobiliary function, other factors altering BA pool size and enterohepatic circulation can affect these levels. To develop fluorescent probes for extracorporeal noninvasive hepatobiliary function assessment by real-time monitoring methods, 1,3-dipolar cycloaddition reactions were used to conjugate near-infrared (NIR) fluorochromes with azide-functionalized BA derivatives (BAD). The resulting compounds (NIRBADs) were chromatographically (FC and PTLC) purified (>95%) and characterized by fluorimetry, 1H NMR, and HRMS using ESI ionization coupled to quadrupole TOF mass analysis. Transport studies using CHO cells stably expressing the BA carrier NTCP were performed by flow cytometry. Extracorporeal fluorescence was detected in anesthetized rats by high-resolution imaging analysis. Three NIRBADs were synthesized by conjugating alkynocyanine 718 with cholic acid (CA) at the COOH group via an ester (NIRBAD-1) or amide (NIRBAD-3) spacer, or at the 3α-position by a triazole link (NIRBAD-2). NIRBADs were efficiently taken up by cells expressing NTCP, which was inhibited by taurocholic acid (TCA). Following i.v. administration of NIRBAD-3 to rats, liver uptake and consequent release of NIR fluorescence could be extracorporeally monitored. This transient organ-specific handling contrasted with the absence of release to the intestine of alkynocyanine 718 and the lack of hepatotropism observed with other probes, such as indocyanine green. NIRBAD-3 administration did not alter serum biomarkers of hepatic and renal toxicity. NIRBADs can serve as probes to evaluate hepatobiliary function by noninvasive extracorporeal methods.

Dihydroartemisinin-Ursodeoxycholic Bile Acid Hybrids in the Fight against SARS-CoV-2

Here, we propose the molecular hybridization of dihydroartemisinin (DHA) and ursodeoxycholic bile acid (UDCA), approved drugs, for the preparation of antiviral agents against SARS-CoV-2. DHA and UDCA were selected on the basis of their recently demonstrated in vitro activity against SARS-CoV-2. A selection of DHA-UDCA-based hybrids obtained by varying the nature of the linkage and the bile acid conjugation point as well as unconjugated DHA and UDCA were tested in vitro for cytotoxicity and anti-SARS-CoV-2 activity on Vero E6 and Calu-3 human lung cells. The hybrid DHA-t-UDCMe, obtained by conjugation via click chemistry on a gram scale, was identified as a potential candidate for SARS-CoV-2 infection treatment due to significant reduction of viral replication, possibly involving ACE2 downregulation, no cytotoxicity, and chemical stability.

Steroid-triazole conjugates: A brief overview of synthesis and their application as anticancer agents

Steroids are biomolecules that play pivotal roles in various physiological and drug discovery processes. Abundant research has been fuelled towards steroid-heterocycles conjugates over the last few decades as potential therapeutic agents against various diseases especially as anticancer agents. In this context various steroid-triazole conjugates have been synthesized and studied for their anticancer potential against various cancer cell lines. A thorough search of the literatures revealed that a concise review pertaining the present topic is not compiled. Therefore, in thus review we summarize the synthesis, anticancer activity against various cancer cell lines and structure activity relationship (SAR) of various steroid-triazole conjugates. This review can lay down the path towards the development of various steroid-heterocycles conjugates with lesser side effects and profound efficacy.

Synthesis and Biological Investigation of Bile Acid-Paclitaxel Hybrids

Chenodeoxycholic acid and ursodeoxycholic acid (CDCA and UDCA, respectively) have been conjugated with paclitaxel (PTX) anticancer drugs through a high-yield condensation reaction. Bile acid-PTX hybrids (BA-PTX) have been investigated for their pro-apoptotic activity towards a selection of cancer cell lines as well as healthy fibroblast cells. Chenodeoxycholic-PTX hybrid (CDC-PTX) displayed cytotoxicity and cytoselectivity similar to PTX, whereas ursodeoxycholic-PTX hybrid (UDC-PTX) displayed some anticancer activity only towards HCT116 colon carcinoma cells. Pacific Blue (PB) conjugated derivatives of CDC-PTX and UDC-PTX (CDC-PTX-PB and UDC-PTX-PB, respectively) were also prepared via a multistep synthesis for evaluating their ability to enter tumor cells. CDC-PTX-PB and UDC-PTX-PB flow cytometry clearly showed that both CDCA and UDCA conjugation to PTX improved its incoming into HCT116 cells, allowing the derivatives to enter the cells up to 99.9%, respect to 35% in the case of PTX. Mean fluorescence intensity analysis of cell populations treated with CDC-PTX-PB and UDC-PTX-PB also suggested that CDC-PTX-PB could have a greater ability to pass the plasmatic membrane than UDC-PTX-PB. Both hybrids showed significant lower toxicity with respect to PTX on the NIH-3T3 cell line.

Bile-Acid-Appended Triazolyl Aryl Ketones: Design, Synthesis, In Vitro Anticancer Activity and Pharmacokinetics in Rats

A library of bile-acid-appended triazolyl aryl ketones was synthesized and characterized by detailed spectroscopic techniques such as ¹H and ¹³C NMR, HRMS and HPLC. All the synthesized conjugates were evaluated for their cytotoxicity at 10 µM against MCF-7 (human breast adenocarcinoma) and 4T1 (mouse mammary carcinoma) cells. In vitro cytotoxicity studies on the synthesized conjugates against MCF-7 and 4T1 cells indicated one of the conjugate 6cf to be most active against both cancer cell lines, with IC₅₀ values of 5.71 µM and 8.71 µM, respectively, as compared to the reference drug docetaxel, possessing IC₅₀ values of 9.46 µM and 13.85 µM, respectively. Interestingly, another compound 6af (IC₅₀ = 2.61 µM) was found to possess pronounced anticancer activity as compared to the reference drug docetaxel (IC₅₀ = 9.46 µM) against MCF-7. In addition, the potent compounds (6cf and 6af) were found to be non-toxic to normal human embryonic kidney cell line (HEK 293), as evident from their cell viability of greater than 86%. Compound 6cf induces higher apoptosis in comparison to 6af (46.09% vs. 33.89%) in MCF-7 cells, while similar apoptotic potential was observed for 6cf and 6af in 4T1 cells. The pharmacokinetics of 6cf in Wistar rats showed an MRT of 8.47 h with a half-life of 5.63 h. Clearly, these results suggest 6cf to be a potential candidate for the development of anticancer agents.

Bile Acid Conjugates with Anticancer Activity: Most Recent Research

The advantages of a treatment modality that combines two or more therapeutic agents in cancer therapy encourages the study of hybrid functional compounds for pharmacological applications. In light of this, we reviewed recent works on hybrid molecules based on bile acids. Due to their biological properties, as well as their different chemical/biochemical reactive moieties, bile acids can be considered very interesting starting molecules for conjugation with natural or synthetic bioactive molecules.

Updates in bile acid-bioactive molecule conjugates and their applications

Bile acid conjugates are emerging as important chemical resources due to their low cost and wide availability of bile acids, making them privileged molecules in drug carrier systems and building blocks for derivatization and chiral template introduction into bioactive molecules. In recent years, bile acids as scaffolds in supramolecular, medicinal, and material chemistry attracted prime focus of researchers as an area of research to be followed with passion. Due to peculiar physicochemical and biological properties, bile acid exhibited various applications in biomedical and pharmaceutical fields. In this review, the bile acid conjugations with different bioactive compounds have been discussed to understand their influence on the bioavailability of bioactive compounds.

Dihydroartemisinin-Bile Acid Hybridization as an Effective Approach to Enhance Dihydroartemisinin Anticancer Activity

A series of hybrid compounds based on natural products-bile acids and dihydroartemisinin-were prepared by different synthetic methodologies and investigated for their in vitro biological activity against HL-60 leukemia and HepG2 hepatocellular carcinoma cell lines. Most of these hybrids presented significantly improved antiproliferative activities with respect to dihydroartemisinin and the parent bile acid. The two most potent hybrids of the series exhibited a 10.5- and 15.4-fold increase in cytotoxic activity respect to dihydroartemisinin alone in HL-60 and HepG2 cells, respectively. Strong evidence that an ursodeoxycholic acid hybrid induced apoptosis was obtained by flow cytometric analysis and western blot analysis.

Clickable conjugates of bile acids and nucleosides: Synthesis, characterization, in vitro anticancer and antituberculosis studies

A series of clickable bile acid-nucleosides conjugates linked directly or via amino acid linker were synthesized, and characterized by spectroscopic techniques such as ¹H NMR, ¹³C NMR, FT-IR, HRMS and HPLC. The synthesized compounds 6a-p were screened for their in vitro anticancer property against a panel of three cancer cell lines (PC-3, MCF-7, IMR-32). In addition, the synthesized derivatives were also tested for their antimycobacterial activity against Mycobacterium tuberculosis H₃₇Rv (ATCC 27294 strain). Among the screened compounds, cholic acid-uridine clicked conjugate (6c), and cholic acid-uridine clicked conjugate liked via phenylalanine moiety (6m) were found to be most active against MCF-7 and IMR-32 exhibiting an IC₅₀ value of 8.084 and 8.71 µM, respectively. The antimycobacterial study of the synthesized conjugates revealed all the conjugates to be active with MIC values in the range of 4.09-15.41 µM. Deoxycholic acid-adenosine clicked conjugate (6b) showed most promising antituberculosis property with MIC value of 4.09 µM. Most of the synthesized conjugates were found to be safe at 50 µM against normal human embryonic kidney (HEK 293 T) cell line.

Fluorous-tag assisted synthesis of bile acid-bisphosphonate conjugates via orthogonal click reactions: an access to potential anti-resorption bone drugs

The synthesis of a small collection of novel bile acid-bisphosphonate (BA-BP) conjugates as potential drug candidates is reported. The disclosed methodology relied on the installation of azide and thiol functionalities at the head and tail positions, respectively, of the BA scaffold and its subsequent decoration by orthogonal click reactions (copper-catalyzed azide-alkyne cycloaddition, thiol-ene or thiol-yne coupling) to introduce BP units and a fluorophore. Because of the troublesome isolation of the target conjugates by standard procedures, the methodology culminated with the functionalization of the BA scaffold with a light fluorous tag to rapidly and efficiently purify intermediates and final products by fluorous solid-phase extraction.

Rational Design of Nucleoside-Bile Acid Conjugates Incorporating a Triazole Moiety for Anticancer Evaluation and SAR Exploration

Herein we report a study on the synthesis and biological evaluation of a library of nucleoside-bile acid conjugates prepared by combining 2′-deoxyadenosine, 2′-deoxyguanosine, 2′-deoxyuridine as well as adenosine and guanosine derivatives with cheno-, urso-, nor-cheno-, nor-urso- and taurourso-desoxycholic acid derivatives by means of the click reaction. The new nucleoside-bile acid conjugates incorporating a triazole moiety were tested in vitro against leukemic K562 and HCT116 colon carcinoma, as well as on normal fibroblast cells. Six compounds displayed interesting anti-proliferative activity against the selected cancer lines and no cytotoxic effects against normal fibroblasts. A possible structure activity relationship was also investigated.

NO Photoreleaser-Deoxyadenosine and -Bile Acid Derivative Bioconjugates as Novel Potential Photochemotherapeutics

This contribution reports the synthesis of some novel bioconjugates with anticancer activity and able to release nitric oxide (NO) under visible light excitation. The 4-nitro-2-(trifluoromethyl)aniline derivative, a suitable NO photodonor, was conjugated with 2'-deoxyadenosine and urso- and cheno-deoxycholic acid derivatives, through a thioalkylic chain or the 4-alkyl-1,2,3-triazole moiety. Photochemical experiments demonstrated the effective release of NO from 2'-deoxyadenosine and ursodeoxycholic acid conjugates under the exclusive control of visible light inputs. Studies for the in vitro antiproliferative activity against leukemic K562 and colon carcinoma HCT116 cell lines are reported for all the compounds as well as a case study of photocytotoxicity against HCT116.