Metabolic activation enhances the cytotoxicity, genotoxicity and mutagenicity of two synthetic alkaloids with selective effects against human tumour cell lines.

The pharmacological potential of drugs must be evaluated to establish their potential therapeutic benefits and side effects. This evaluation includes assessment of the effects of hepatic enzymes that catalyse their metabolic activation. Previously, our research group synthesized and characterized a set of synthetic 3-alkyl pyridine alkaloid (3-APA) analogues that cause in vitro cytotoxic, genotoxic, and mutagenic effects in various human cancer cell lines. The present study aimed to evaluate these activities with the two most promising synthetic 3-APAs (3-APA 1 and 3-APA 2) against cell lines derived from breast cancer (MDA-MB-231), ovarian cancer (TOV-21 G) and lung fibroblasts (WI-26-VA4) with and without metabolic activation (S9 fraction). The cytotoxicity of the compounds was evaluated employing MTT and clonogenic assays. In addition, comet assays, γH2AX immunocytochemistry labelling assays and cytokinesis-block micronucleus tests were carried out to evaluate the potential of these compounds to induce chromosomal damage. The results obtained in the MTT assay showed that compound 3-APA 2 exhibited high selectivity index (SI) values (ranging between 21.0 and 92.6). In addition, the cytotoxicity of the compounds was clearly enhanced by metabolic activation. Moreover, both compounds were genotoxic and induced double-strand breaks in DNA and chromosomal lesions with and without S9. The cancer cell lines tested showed higher genotoxic sensitivity to the compounds than did the non-tumour cell line used as a reference. The genotoxic and mutagenic effects of the compounds were potentiated in experiments with metabolic activation. The data obtained in this study indicate that compound 3-APA 2 is more active against the human cancer cell lines tested, both with and without metabolic activation, and can therefore be considered a candidate drug to treat human ovarian and breast cancer.

Target-Guided Synthesis and Antiplasmodial Evaluation of a New Fluorinated 3-Alkylpyridine Marine Alkaloid Analog.

The need to develop new alternatives for antimalarial treatment is urgent. Herein, we report the synthesis and antimalarial evaluation of a small library of synthetic 3-alkylpyridine marine alkaloid (3-APA) analogs. First, the compounds were evaluated in vitro against Plasmodium falciparum. The most active compound 5c was selected for optimization of its antimalarial properties. An in silico approach was used based on pure ab initio electronic structure prediction, and the results indicated that a substitution of the hydroxyl group by a fluorine atom could favor a more stable complex with heme at a molecular ratio of 2:1 (heme/3-APA halogenated). A new fluorinated 3-APA analog was synthesized (compound 7), and its antimalarial activity was re-evaluated. Compound 7 exhibited optimized antimalarial properties (P. falciparum IC50 = 2.5 µM), low genotoxicity, capacity to form a more stable heme/3-APA complex at a molecular ratio of 2:1, and conformity to RO5. The new compound, therefore, has great potential as a new lead antimalarial agent.

New 3-alkylpyridine marine alkaloid analogues as promising antitumor agents against the CD44+/high /CD24-/low subset of triple-negative breast cancer cell line.

Triple-negative breast cancer (TNBC) is one of the most aggressive cancers in women. Additionally, presence of residual cancer stem cells (CSC) in TNBC has challenged the efficacy of chemotherapy. Thus, the development of new molecules with potential action against CSC is fundamental. In this study, six synthetic analogues of theonelladin C, a 3-alkylpyridine marine alkaloid, were tested for cytotoxic activity against human TNBC cell line (BT-549) and tumorspheres derived from BT-549. Cytotoxicity assay was performed by sulforhodamine B (SRB). BT-549 and tumorspheres were examined for CD44+/high /CD24-/low markers, indicative of CSC profile, by flow cytometry. Clonogenic assay was performed to verify inhibiting growth of tumorspheres by the synthetic analogues. Cell death by apoptosis was investigated employing annexin V assay. SRB assay on BT-549 cells revealed that compounds 1c and 2c were the most active of the series, with IC50 values of 18.66 and 9.8 µm, respectively. Compounds 1c and 2c were able to reduce both CSC-like population (CD44+/high /CD24-/low ) and non-CSC population (CD44+/high /CD24+/high ) in tumorsphere model. Clonogenic and annexin V assays confirmed the ability of 1c and 2c to induce growth inhibition and apoptosis in BT-549 cells and tumorspheres. These preliminary data indicate that these compounds are a promising class for development of anticancer agents.

Synthesis and biological evaluation of novel 3-alkylpyridine marine alkaloid analogs with promising anticancer activity.

Cancer continues to be one of the most important health problems worldwide, and the identification of novel drugs and treatments to address this disease is urgent. During recent years, marine organisms have proven to be a promising source of new compounds with action against tumoral cell lines. Here, we describe the synthesis and anticancer activity of eight new 3-alkylpyridine alkaloid (3-APA) analogs in four steps and with good yields. The key step for the synthesis of these compounds is a Williamson etherification under phase-transfer conditions. We investigated the influence of the length of the alkyl chain attached to position 3 of the pyridine ring on the cytotoxicity of these compounds. Biological assays demonstrated that compounds with an alkyl chain of ten carbon atoms (4c and 5c) were the most active against two tumoral cell lines: RKO-AS-45-1 and HeLa. Micronucleus and TUNEL assays showed that both compounds are mutagenic and induce apoptosis. In addition, Compound 5c altered the cellular actin cytoskeleton in RKO-AS-45-1 cells. The results suggest that Compounds 4c and 5c may be novel prototype anticancer agents.