A straightforward approach toward cytotoxic pyrrolidine alkaloids: Novel analogues of natural broussonetines

A simple approach to orthogonally protected 2,3-diaminopropanols: intermediates for l- and d-Dap-containing peptidomimetics

A simple approach to orthogonally protected 2,3-diaminopropanols from easily available d- and l-erythrofuranose has been accomplished. The pivotal step involved a cascade Overman rearrangement to install two novel C-N bonds and create the desired diamino alcohol motif, while a one-pot ozonolysis/reductive workup accompanied by the rational execution of suitable functional group transformations allowed the carbon skeleton of the target compounds to be completed. A series of the synthesised diaminopropanols was evaluated regarding their capacity to alter proliferation of selected cancer cell lines.

Pyrrolidine SS13 induces oxidative stress and autophagy-mediated cell death in colorectal cancer cells

INTRODUCTION

Pyrrolidines, nitrogenous organic compounds, are among the most intensively studied agents because of their antibacterial, antiviral, neurological, and promising antitumor effects. Moreover, many medicinal drugs contain pyrrolidine moiety such as sunitinib (anticancer drug), telaprevir and ombitasvir (antiviral drugs) or ramipril (antihypertensive drug).

RATIONALE OF THE STUDY

Based on the pro-apoptotic effect of pyrrolidine SS13, this study focuses on the pro-oxidative properties of the tested pyrrolidine SS13 on colorectal cancer cells to deepen the understanding of its mechanisms of action.

RESEARCH HYPOTHESIS

We hypothesize that SS13 induces oxidative stress and autophagy activation in HCT116 and Caco-2 cell lines, thus contributing to antiproliferative effects.

METHODS

Flow cytometry, western blot, fluorescence microscopy and qRT-PCR were used to evaluate the effect of pyrrolidine SS13.

CONCLUSION AND FUTURE DIRECTIONS

Pyrrolidine SS13 induced oxidative stress through the accumulation of reactive oxygen and nitrogen species in both cell lines and the modulation of both superoxide dismutase isoenzymes (SOD1, SOD2). Oxidative stress was also associated with the activation of DNA damage response system and modulation of stress/survival pathways. We demonstrated for the first time that pyrrolidine SS13 is involved in the induction of autophagy accompanied by increased levels of autophagic markers (p-AMPK, p-ULK, LC3I/II and ATG7) and a significant decrease in p62 protein levels in both cell lines. Finally, chloroquine, an inhibitor of autophagy, enhanced cell survival and suppressed the cytotoxic effect of SS13 in HCT116 and Caco-2 cells, indicating that SS13 contributes to autophagy-mediated cell death. Taken together, our results suggest that oxidative stress and autophagy participate in the antiproliferative effect of pyrrolidine SS13 on colorectal cancer cells. Further research using primary cell cultures obtained from different animal tissues as well as performing in vivo experiments is needed to understand these processes in detail and to investigate the potential therapeutic application of new pyrrolidine derivatives.

A 'Chiron' approach to novel phytosphingosine mimetics based on a cascade [3,3]-sigmatropic rearrangement

Straightforward access to enantiomerically pure 3,4-diamino-3,4-dideoxyphytosphingosines, as novel analogues of natural d-ribo-phytosphingosine was accomplished, starting from two available chirons: dimethyl l-tartrate and d-isoascorbic acid. A sequential Overman rearrangement followed by late-stage introduction of the alkyl side chain moiety via olefin cross-metathesis is the cornerstone of this approach. The preliminary evaluation study of the synthesised sphingomimetics, based on their ability to inhibit a proliferation of human cancer cells, showed promising cytotoxicity against Jurkat and HeLa cells for (2R,3R,4S)-2,3,4-triaminooctadecan-1-ol trihydrochloride.

Involvement of Both Extrinsic and Intrinsic Apoptotic Pathways in Tridecylpyrrolidine-Diol Derivative-Induced Apoptosis In Vitro

Despite the decreasing trend in mortality from colorectal cancer, this disease still remains the third most common cause of death from cancer. In the present study, we investigated the antiproliferative and pro-apoptotic effects of (2S,3S,4R)-2-tridecylpyrrolidine-3,4-diol hydrochloride on colon cancer cells (Caco-2 and HCT116). The antiproliferative effect and IC₅₀ values were determined by the MTT and BrdU assays. Flow cytometry, qRT-PCR and Western blot were used to study the cellular and molecular mechanisms involved in the induction of apoptotic pathways. Colon cancer cell migration was monitored by the scratch assay. Concentration-dependent cytotoxic and antiproliferative effects on both cell lines, with IC₅₀ values of 3.2 ± 0.1 μmol/L (MTT) vs. 6.46 ± 2.84 μmol/L (BrdU) for HCT116 and 2.17 ± 1.5 μmol/L (MTT) vs. 1.59 ± 0.72 μmol/L (BrdU), for Caco-2 were observed. The results showed that tridecylpyrrolidine-induced apoptosis was associated with the externalization of phosphatidylserine, reduced mitochondrial membrane potential (MMP) accompanied by the activation of casp-3/7, the cleavage of PARP and casp-8, the overexpression of TNF-α and FasL and the dysregulation of Bcl-2 family proteins. Inhibition of the migration of treated cells across the wound area was detected. Taken together, our data show that the anticancer effects of tridecylpyrrolidine analogues in colon cancer cells are mediated by antiproliferative activity, the induction of both extrinsic and intrinsic apoptotic pathways and the inhibition of cell migration.

Straightforward access to novel cytotoxic phytosphingosine-like aminotriols from l-erythrose chiron

A divergent approach to a small library of long-chain 6-amino-1,4,5-triols as novel phytosphingosine-type entities, together with their preliminary cytotoxic evaluation, was achieved. Construction of the target compounds addressed two key aspects. First, the installation of a carbon-nitrogen bond via two prototypes of [3,3]-sigmatropic rearrangements and second the introduction of an alkyl side chain unit by using a late stage olefin cross-metathesis process. As shown in cell viability experiments, the corresponding HCl salts proved to be the most cytotoxic derivatives among all the tested substances, with IC₅₀ values in the lower micromolar range on the Jurkat, HeLa and HCT-116 cell lines.