Norbornene and Related Structures as Scaffolds in the Search for New Cancer Treatments

The norbornene scaffold has arisen as a promising structure in medicinal chemistry due to its possible therapeutic application in cancer treatment. The development of norbornene-based derivatives as potential chemotherapeutic agents is attracting significant attention. Here, we report an unprecedented review on the recent advances of investigations into the antitumoral efficacy of different compounds, including the abovementioned bicyclic scaffold in their structure, in combination with chemotherapeutic agents or forming metal complexes. The impact that structural modifications to these bicyclic compounds have on the antitumoral properties and the mechanisms by which these norbornene derivatives act are discussed in this review. In addition, the use of norbornene, and its related compounds, encapsulation in nanosystems for its use in cancer therapies is here detailed.

Application of Amino Acids in the Structural Modification of Natural Products: A Review

Natural products and their derivatives are important sources for drug discovery; however, they usually have poor solubility and low activity and require structural modification. Amino acids are highly soluble in water and have a wide range of activities. The introduction of amino acids into natural products is expected to improve the performance of these products and minimize their adverse effects. Therefore, this review summarizes the application of amino acids in the structural modification of natural products and provides a theoretical basis for the structural modification of natural products in the future. The articles were divided into six types based on the backbone structures of the natural products, and the related applications of amino acids in the structural modification of natural products were discussed in detail.

Dirhodium Coordination Polymers for Asymmetric Cyclopropanation of Diazooxindoles with Olefins: Synthesis and Spectroscopic Analysis

A facile approach is reported for the preparation of dirhodium coordination polymers [Rh₂ (L1)₂ ]_n (Rh₂ -L1) and [Rh₂ (L2)₂ ]_n (Rh₂ -L2; L1=N,N'-(pyromellitoyl)-bis-L-phenylalanine diacid anion, L2=bis-N,N'-(L-phenylalanyl) naphthalene-1,4,5,8-tetracarboxylate diimide) from chiral dicarboxylic acids by ligand exchange. Multiple techniques including FTIR, XPS, and ¹ H→¹³ C CP MAS NMR spectroscopy reveal the formation of the coordination polymers. ¹⁹ F MAS NMR was utilized to investigate the remaining TFA groups in the obtained coordination polymers, and demonstrated near-quantitative ligand exchange. DR-UV-vis and XPS confirm the oxidation state of the Rh center and that the Rh-single bond in the dirhodium node is maintained in the synthesis of Rh₂ -L1 and Rh₂ -L2. Both coordination polymers exhibit excellent catalytic performance in the asymmetric cyclopropanation reaction between styrene and diazooxindole. The catalysts can be easily recycled and reused without significant reduction in their catalytic efficiency.

Norbornene chaotropic salts as low molecular mass ionic organogelators (LMIOGs)

Phenylalanine functionalised norbornene (9:Na) functions as a potent, low molecular-mass (MW = 333 Da) ionic organogelator with a minimum gelating concentration of 0.5 wt% in THF, i-PrOH, 1,4-dioxane and n-BuOH. Fibrous crystals form in the gel and X-ray crystallography identified a cation mediated helical assembly process controlled by the chirality of the phenylalanine. In addition to excellent gelating properties 9:Na readily forms aqueous biphasic and triphasic systems.

Naphthoquinones: A continuing source for discovery of therapeutic antineoplastic agents

Naturally occurring naphthoquinones, usually in forms of botanical extracts, have been implicated with human life since ancient time, far earlier than their isolation and identification in modern era. The long use history of naphthoquinones has witnessed their functional shift from the original purposes as dyes and ornaments toward medicinal benefits. Hitherto, numerous studies have been carried out to elucidate the pharmacological profile of both natural and artificial naphthoquinones. A number of entities have been identified with promising therapeutic potential. Apart from the traditional effects of wound healing, anti-inflammatory, hemostatic, antifertility, insecticidal and antimicrobial, etc., the anticancer potential of naphthoquinones either in combination with other treatment approaches or on their own is being more and more realized. The molecular mechanisms of naphthoquinones in cells mainly fall into two categories as inducing oxidant stress by ROS (reactive oxygen species) generation and directly interacting with traditional therapeutic targets in a non-oxidant mechanism. Based on this knowledge, optimized agents with naphthoquinones scaffold have been acquired and further tested. Hereby, we summarize the explored biological mechanisms of naphthoquinones in cells and review the application perspective of promising naphthoquinones in cancer therapies.

Antiviral activity of a synthesized shikonin ester against influenza A (H1N1) virus and insights into its mechanism

This study aimed to examine the antiviral effects of shikonin ester ((R)-1-(5, 8-dihydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-4-methylpent-3-en-1-yl3-(1H- indol-3-yl) propanoate (PMM-034) against influenza A (H1N1) virus. We investigated PMM-034 anti-H1N1 activity and its effect on caspase 3 gene expression during cellular apoptosis after influenza virus infection in vitro. Neuraminidase (NA) inhibition was assessed in comparison with oseltamivir in the influenza virus standard strains A/PR/8/34 to understand the viral mechanism. MDCK and A549 cells were used to investigate influenza viral infection and the structure-activity relationship between PMM-034 and NA was evaluated by pharmacophore-based docking modeling. The production of viral protein was tested by western blot. A/PR/8/34 induced cell inhibition but this was reduced by PMM-034 to 16μg/mL and this showed a selective index of 10mM. PMM-034 inhibited NA in a dose dependent manner, similar to oseltamivir inhibition. A sharp decrease in viral nucleocapsid protein mRNA was observed in infected cells after treatment with PMM-034. Apoptosis of infected A459 cells was inhibited by PMM-034 with decreased caspase 3 levels. ARG 118, ARG 152, ARG 371 and GLU 227 in the binding pocket of NA bound to PMM-034 in the docking model. Taken together, these results suggest PMM-034 shikonin ester blocked H1N1 infection and might be a potential anti-H1N1 drug.

Design, Synthesis, and Biological Evaluation of Chalcone-Containing Shikonin Derivatives as Inhibitors of Tubulin Polymerization

The biological importance of microtubules in mitosis makes them an interesting target for the development of anticancer agents. In this study, a series of novel chalcone-containing shikonin derivatives was designed, synthesized, and evaluated for biological activities. Among them, derivative PMMB-259 [(R)-1-(5,8-dihydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-4-methylpent-3-en-1-yl (E)-2-(4-(3-oxo-3-(3-(trifluoromethoxy)phenyl)prop-1-en-1-yl)phenoxy)acetate] was identified as a potent inhibitor of tubulin polymerization. Further investigation confirmed that PMMB-259 can induce MCF-7 cell apoptosis, reduce the mitochondrial transmembrane potential, and arrest the cell cycle at the G₂ /M phase. Moreover, the morphological variation of treated cells was visualized by confocal microscopy. The results, along with docking simulations, further indicated that PMMB-259 can bind well to tubulin at the colchicine site. Overall, these studies may provide a new molecular scaffold for the further development of antitumor agents that target tubulin.

Synthesis and biological evaluation of bivalent β-carbolines as potential anticancer agents

A series of novel bivalent β-carbolines were synthesized and evaluated for their anti-proliferative activities on a panel of cancer cell lines, apoptosis induction and cell cycle effects.