Exploring the Antiviral Potential of Natural Compounds against Influenza: A Combined Computational and Experimental Approach.

The influenza A virus nonstructural protein 1 (NS1), which is crucial for viral replication and immune evasion, has been identified as a significant drug target with substantial potential to contribute to the fight against influenza. The emergence of drug-resistant influenza A virus strains highlights the urgent need for novel therapeutics. This study proposes a combined theoretical criterion for the virtual screening of molecular libraries to identify candidate NS1 inhibitors. By applying the criterion to the ZINC Natural Product database, followed by ligand-based virtual screening and molecular docking, we proposed the most promising candidate as a potential NS1 inhibitor. Subsequently, the selected natural compound was experimentally evaluated, revealing measurable virus replication inhibition activity in cell culture. This approach offers a promising avenue for developing novel anti-influenza agents targeting the NS1 protein.

Synthesis and Structure-Activity Relationship Studies of C(13)-Desmethylene-(-)-Zampanolide Analogs.

We describe the synthesis and biochemical and cellular profiling of five partially reduced or demethylated analogs of the marine macrolide (-)-zampanolide (ZMP). These analogs were derived from 13-desmethylene-(-)-zampanolide (DM-ZMP), which is an equally potent cancer cell growth inhibitor as ZMP. Key steps in the synthesis of all compounds were the formation of the dioxabicyclo[15.3.1]heneicosane core by an intramolecular HWE reaction (67-95 % yield) and a stereoselective aza-aldol reaction with an (S)-BINOL-derived sorbamide transfer complex, to establish the C(20) stereocenter (24-71 % yield). As the sole exception, for the 5-desmethyl macrocycle, ring-closure relied on macrolactonization; however, elaboration of the macrocyclization product into the corresponding zampanolide analog was unsuccessful. All modifications led to reduced cellular activity and lowered microtubule-binding affinity compared to DM-ZMP, albeit to a different extent. For compounds incorporating the reactive enone moiety of ZMP, IC50 values for cancer cell growth inhibition varied between 5 and 133 nM, compared to 1-12 nM for DM-ZMP. Reduction of the enone double bond led to a several hundred-fold loss in growth inhibition. The cellular potency of 2,3-dihydro-13-desmethylene zampanolide, as the most potent analog identified, remained within a ninefold range of that of DM-ZMP.

The Pictet-Spengler Reaction Updates Its Habits.

The Pictet-Spengler reaction (P-S) is one of the most direct, efficient, and variable synthetic method for the construction of privileged pharmacophores such as tetrahydro-isoquinolines (THIQs), tetrahydro-ß-carbolines (THBCs), and polyheterocyclic frameworks. In the lustro (five-year period) following its centenary birthday, the P-S reaction did not exit the stage but it came up again on limelight with new features. This review focuses on the interesting results achieved in this period (2011-2015), analyzing the versatility of this reaction. Classic P-S was reported in the total synthesis of complex alkaloids, in combination with chiral catalysts as well as for the generation of libraries of compounds in medicinal chemistry. The P-S has been used also in tandem reactions, with the sequences including ring closing metathesis, isomerization, Michael addition, and Gold- or Brønsted acid-catalyzed N-acyliminium cyclization. Moreover, the combination of P-S reaction with Ugi multicomponent reaction has been exploited for the construction of highly complex polycyclic architectures in few steps and high yields. The P-S reaction has also been successfully employed in solid-phase synthesis, affording products with different structures, including peptidomimetics, synthetic heterocycles, and natural compounds. Finally, the enzymatic version of P-S has been reported for biosynthesis, biotransformations, and bioconjugations.

A promising natural product, pristimerin, results in cytotoxicity against breast cancer stem cells in vitro and xenografts in vivo through apoptosis and an incomplete autopaghy in breast cancer.

Several natural products have been suggested as effective agents for the treatment of cancer. Given the important role of CSCs (Cancer Stem Cells) in cancer, which is a trendy hypothesis, it is worth investigating the effects of pristimerin on CSCs as well as on the other malignant cells (MCF-7 and MDA-MB-231) of breast cancer. The anti-growth activity of pristimerin against MCF-7 and MCF-7s (cancer stem cell enriched population) cells was investigated by real time viability monitorization (xCELLigence System®) and ATP assay, respectively. Mode of cell death was evaluated using electron and fluorescence microscopies, western blotting (autophagy, apoptosis and ER-stress related markers) and flow cytometry (annexin-V staining, caspase 3/7 activity, BCL-2 and PI3K expressions). Pristimerin showed an anti-growth effect on cancer cells and cancer stem cells with IC50 values ranging at 0.38-1.75µM. It inhibited sphere formation at relatively lower doses (<1.56µM). Apoptosis was induced in MCF-7 and MCF-7s cells. In addition, extensive cytoplasmic vacuolation was observed, implying an incompleted autophagy as evidenced by the increase of autophagy-related proteins (p62 and LC3-II) with an unfolded protein response (UPR). Pristimerin inhibited the growth of MCF-7 and MDA-MB-231-originated xenografts in NOD.CB17-Prkdcscid/J mice. In mice, apoptosis was further confirmed by cleavage of PARP, activation of caspase 3 and/or 7 and TUNEL staining. Taken together, pristimerin shows cytotoxic activity on breast cancer both in vitro and in vivo. It seems to represent a robust promising agent for the treatment of breast cancer. Pristimerin's itself or synthetic novel derivatives should be taken into consideration for novel potent anticancer agent(s).

Synthesis, biological evaluation and molecular modeling studies on novel quinonoid inhibitors of CDC25 phosphatases.

The cell division cycle 25 phosphatases (CDC25A, B, and C; E.C. 3.1.3.48) are key regulator of the cell cycle in human cells. Their aberrant expression has been associated with the insurgence and development of various types of cancer, and with a poor clinical prognosis. Therefore, CDC25 phosphatases are a valuable target for the development of small molecule inhibitors of therapeutic relevance. Here, we used an integrated strategy mixing organic chemistry with biological investigation and molecular modeling to study novel quinonoid derivatives as CDC25 inhibitors. The most promising molecules proved to inhibit CDC25 isoforms at single digit micromolar concentration, becoming valuable tools in chemical biology investigations and profitable leads for further optimization. [Formula: see text].

Occurrence of Enantioselectivity in Nature: The Case of (S)-Norcoclaurine.

This review article is aimed at providing a monographic overview on (S)-norcoclaurine (NC) alkaloid from three diverse points of view, collected all together for the first time: 1) the synthetic one, where the compound is seen as a target chiral molecule to be obtained in the highest optical purity and as a starting point for the development of biocatalytic asymmetric syntheses of tetrahydroisoquinoline alkaloids; 2) the chromatographic one, which addresses the HPLC separation of the two NC enantiomers; and 3) the biochemical one, for which a thorough understanding of the topology and mechanism of action of norcoclaurine synthase (NCS) enzyme is still a matter of debate. Special emphasis on the most recent studies in the field is given by discussing the results published by the main research groups who are working on NC and NCS.

A Method for the Stereoselective Construction of the Hemiaminal Center in Zampanolides.

We have developed a new method for the stereoselective establishment of the N-acyl hemiaminal moiety in zampanolide-type structures that involves the reaction of (Z,E)-sorbamide (3) with BINAL-H and subsequent amide transfer from a putative aluminum carboximidoate complex to the aldehyde moiety of a dactylolide precursor, such as 2 or 5. The method has enabled the efficient synthesis of 13-desmethylene-(-)-zampanolide (4), which was found to be an equipotent cell growth inhibitor as the natural product (-)-zampanolide (1).

Structural Elucidation and Antimicrobial Characterization of Novel Diterpenoids from Fabiana densa var. ramulosa.

Novel diterpenoids were isolated from the extracts of Fabiana densa var. ramulosa and found to display a selective activity against Gram-positive bacterial strains with negligible cytotoxicity toward human keratinocytes. This study highlighted the role played by the acidic group at C18 of the tetracyclic ent-beyerene scaffold for antibacterial effects and how the length and flexibility of the alkyl chain between the two carbonyl groups are crucial factors to increase the antimicrobial activity of the molecules, supporting the development of natural products from F. densa and their derivatives for treatment of microbial infections.

Synergistic inhibition of the Hedgehog pathway by newly designed Smo and Gli antagonists bearing the isoflavone scaffold.

Aberrant activation of the Hedgehog (Hh) pathway is responsible for the onset and progression of several malignancies. Small molecules able to block the pathway at the upstream receptor Smoothened (Smo) or the downstream effector Gli1 have thus emerged recently as valuable anticancer agents. Here, we have designed, synthesized, and tested new Hh inhibitors taking advantage by the highly versatile and privileged isoflavone scaffold. The introduction of specific substitutions on the isoflavone's ring B allowed the identification of molecules targeting preferentially Smo or Gli1. Biological assays coupled with molecular modeling corroborated the design strategy, and provided new insights into the mechanism of action of these molecules. The combined administration of two different isoflavones behaving as Smo and Gli antagonists, respectively, in primary medulloblastoma (MB) cells highlighted the synergistic effects of these agents, thus paving the way to further and innovative strategies for the pharmacological inhibition of Hh signaling.

Polymeric glabrescione B nanocapsules for passive targeting of Hedgehog-dependent tumor therapy in vitro.

AIM: With the purpose of delivering high doses of glabrescione B (GlaB) to solid tumors after systemic administration, long-circulating GlaB-loaded oil-cored polymeric nanocapsules (NC-GlaB) were formulated. MATERIALS & METHODS: Synthesis of GlaB and its encapsulation in nanocapsules (NCs) was performed. Empty and GlaB-loaded NCs were assessed for their physico-chemical properties, in vitro cytotoxicity and in vivo biodistribution. RESULTS: GlaB was efficiently loaded into NCs (∽90%), which were small (∽160 nm), homogeneous and stable upon storage. Further, GlaB and NC-GlaB demonstrated specific activities against the cancer stem cells. Preliminary studies in tumor-bearing mice supported the ability of NC to accumulate in pancreatic tumors. CONCLUSION: This study provides early evidence that NC-GlaB has the potential to be utilized in a preclinical setting and justifies the need to perform therapeutic experiments in mice.

One Hundred Faces of Cyclopamine.

The natural steroidal alkaloid cyclopamine has been identified as the first inhibitor of the Hedgehog (Hh) signaling pathway, which is implicated in embryonic development and tumorigenesis, as well as is hyperactivated in cancer stem cells (CSCs). The list of Hh-dependent tumors is steadily growing, and it has been estimated that about 25% of all cancer deaths show signs of aberrant Hh pathway activation. Notably, cyclopamine has been found to exert anticancer activity against several types of human cancer and to inhibit CSCs proliferation, thus highlighting the druggability of the Hh pathway and paving new opportunities in anticancer drug discovery. The aim of the present work is to review the main synthetic strategies to cyclopamine and its derivatives, with particular emphasis on the challenging chemical modifications aimed at improving the biological activity of the molecule.

The plant-derived triterpenoid tingenin B is a potent anticancer agent due to its cytotoxic activity on cancer stem cells of breast cancer in vitro.

Despite the rapid advances in chemotherapy regimens, the outcome of patients with breast cancer is not satisfactory. One of the reasons of this dissatisfaction is that subsets of cells in tumors which referred as cancer stem cells (CSCs) show and/or gain resistance to therapies. Thus, compounds that target CSCs are urgently needed. Since some are already used in the clinic, natural products have great potential for further development as anti cancer drugs. The aim of this study is to investigate the cytotoxic activity of tingenin b (or 22ß-hydroxytingenone) which is a quinone-methide triterpenoid structurally related to tingenone, against breast CSCs (stem-cell enriched population from MCF-7 cell line, MCF-7s). It has been found that tingenin b was cytotoxic against MCF-7s (IC50 value for 48 h was found to be 2.38 µM) by inducing apoptosis. It was evident by Annexin V staining positivity, decreased mitochondrial membrane potential and Bcl-2 dephosphorylation with a concomitant increase in Bax protein expression. In addition, endoplasmic reticulum stress was also found to be involved in tingenin b-induced cell death. In conclusion, the results warrant further studies aimed at elucidating and corroborating its possible use in the treatment of breast cancer.

The Pictet-Spengler Reaction Still on Stage.

Today, in spite of being older than a century (born in 1911), the Pictet-Spengler two component reaction (PS-2CR) is still one of the most popular reactions, not only for the synthesis of tetrahydroisoquinolines (THIQs), tetrahydro-ß-carbolines (THBCs), or more complex structures containing these two privileged moieties, but also for the construction of novel scaffolds, available for structure-activity relationship (SAR) studies and/or for combinatorial libraries targeted at drug discovery. The prominence of the P-S cyclization is brought about by the inheritance from analogous enzyme-catalyzed reactions of the biogenetic pathways of natural products, mainly indole alkaloids, with a broad range of biological activities. This knowledge has been the starting point for the biomimetic synthesis or the bio-engineering production of pharmacologically important drugs. The long-lasting life of the P-S reaction depends on the discovery of its multiple facets, the modifications of its parameters and components, as well as the continuous renovation of solutions for the challenging stereochemical outcome of the transformation. This paper deals with an updated visit to the P-S reaction aiming to find the threads of the story without forgetting the numerous facets of the prism. It is organized as a theater piece, with a prologue and the main scene (namely, Act 1) where the readers can follow the parade of the two above-mentioned very recurring motifs (namely, THIQ and THBC) by moving from one step to another (a cyclization, an intramolecular attack, a stereoselective passage) to find the way out of the labyrinth of the P-S reaction.