A set of styrylpyridinium (SP) compounds was synthesised in order to study their spectroscopic and cell labelling properties. The compounds comprised different electron donating parts (julolidine, p-dimethylaminophenyl, p-methoxyphenyl, 3,4,5-trimethoxyphenyl), conjugated linkers (vinyl, divinyl), and an electron-withdrawing N-alkylpyridinium part. Geminal or bis-compounds incorporating two styrylpyridinium (bis-SP) moieties at the 1,3-trimethylene unit were synthesised. Compounds comprising a divinyl linker and powerful electron-donating julolidine donor parts possessed intensive fluorescence in the near-infrared region (maximum at ~760 nm). The compounds had rather high cytotoxicity towards the cancerous cell lines HT-1080 and MH-22A; at the same time, basal cytotoxicity towards the NIH3T3 fibroblast cell line ranged from toxic to harmful. SP compound 6e had IC50 values of 1.0 ± 0.03 µg/mL to the cell line HT-1080 and 0.4 µg/mL to MH-22A; however, the basal toxicity LD50 was 477 mg/kg (harmful). The compounds showed large Stokes’ shifts, including 195 nm for 6a,b, 240 nm for 6e, and 325 and 352 nm for 6d and 6c, respectively. The highest photoluminescence quantum yield (PLQY) values were observed for 6a,b, which were 15.1 and 12.2%, respectively. The PLQY values for the SP derivatives 6d,e (those with a julolidinyl moiety) were 0.5 and 0.7%, respectively. Cell staining with compound 6e revealed a strong fluorescent signal localised in the cell cytoplasm, whereas the cell nuclei were not stained. SP compound 6e possessed self-assembling properties and formed liposomes with an average diameter of 118 nm. The obtained novel data on near-infrared fluorescent probes could be useful for the development of biocompatible dyes for biomedical applications.

Breast cancer is the most common invasive cancer and colorectal cancer (CRC) the second most diagnosed malignancy in women worldwide. In men CRC is the third most common cancer. Despite the recent advances in targeted therapy, the clinical efficacy is often limited, noncurative, with a high toxicity profile, and exorbitant costs. Therefore, there is a growing interest in identifying natural compounds that are safe and affordable as adjunctive treatments to the conventional therapy currently offered for these patients. Curcumin from the roots of the Curcuma longa, is one such compound that has become one of the leading and most studied natural medicines for its role in cancer prevention and powerful antioxidant activity. However, its fast metabolism, low bioavailability, and the lack of specificity call for curcumin analogues to be synthesized with increased potency and higher specificity. In search of lead compounds in the present study the cytotoxic effects of curcumin and 14 heterocyclic curcumin derivatives have been screened using the MTT assay on two cancer cell lines HCT-116 and MDA-MB-231 and also on the normal GM08402 (human fibroblast) cell line. Electrochemical oxidation potentials were determined for selected compounds to reveal their electron-donating capacity and as a general indicator of their radical scavenging ability. Two dihydropyridone lead compounds have been identified which compared to curcumin have higher cytotoxicity on both cancer cell lines and at the same time with reduced cytotoxicity on the normal cell line.

Acyl derivatives of aziridine-2-carboxylic acid have been synthesized and tested as PDIA1 inhibitors. Calculations of charge value and distribution in aziridine ring system and some alkylating agents were performed. For the first time was found that acyl derivatives of aziridine-2-carboxylic acid are weak to moderately active PDIA1 inhibitors.

Selenophenoquinolinone is a prospective scaffold for the development of ABCB1 inhibitors for the treatment of MDR cancers.

Synthetic procedures for the preparation of selenophenochromones by treating ethynyl chromones with selenium halides were elaborated. Methyl 3-bromo-2-(1-hydroxycyclohexyl)-9-oxo-9H-selenopheno[2,3-f]chromene-7-carboxylate exhibits high selective in vitro cytotoxic activity against human lung carcinoma cells A549 and H69 up to 1.2 μM.

A set of six new 4-pyridinio-1,4-dihydropyridine (1,4-DHP) compounds has been synthesized. The calcium channel modulating activity of these compounds was evaluated in an aorta vascular smooth muscle cell line (A7R5), in an isolated rat aortic ring model, and in human neuroblastoma cell lines (SH-SY5Y). The antagonistic effect of these 1,4-DHP was tested by modulating the impact of carbachol-dependent mobilization of intracellular Ca2+ in SH-SY5Y cells. The intracellular free Ca2+ concentration was measured in confluent monolayers of SH-SY5Y cells and A7R5 cells with the Ca2+-sensitive fluorescent indicator Fluo-4 NW. Only four compounds showed calcium channel blocking activity in SH-SY5Y and A7R5 cells as well as in the aortic ring model. Among them, compound 3 was the most active calcium channel antagonist, which had 3 times higher activity on carbachol-activated SH-SY5Y cells than amlodipine. Two of the compounds were inactive. Compound 4 had 9 times higher calcium agonist activity than the classic DHP calcium agonist Bay K8644. The intracellular mechanism for the action of compound 4 using inhibitor analysis was elucidated. Nicotinic as well as muscarinic receptors were not involved. Sarcoplasmic reticulum (ER) Ca2+ (SERCA) stores were not affected. Ryanodine receptors (RyRs), another class of intracellular Ca2+ releasing channels, participated in the agonist response evoked by compound 4. The electrooxidation data suggest that the studied compounds could serve as antioxidants in OS.

This study was designed to develop a fast and convenient methodology for the preparation of 10-nonyl acridine orange (NAO) and its silyl analogues to improve their photo-physical properties for the detection and quantification of cardiolipin (CL).

Synthetic procedures for the preparation of 8-ethynylxanthines by treating 8-bromocaffeine and 8-bromopentoxifylline with terminal acetylenes were elaborated. Certain ethynylxanthine derivatives exhibit high in vitro antiproliferative activity against a panel of cancer cell lines, matrix metalloproteinase and in vitro angiogenesis inhibitory activity. Ca2+ channel blocking and agonist activity of the synthesized ethynylxanthines was discussed based on data obtained on the H9C2, SH-SY5Y, and A7R5 cell lines.

The development of targeted drugs for the treatment of cancer remains an unmet medical need. This study was designed to investigate the mechanism underlying breast cancer cell growth suppression caused by fused isoselenazolium salts. The ability to suppress the proliferation of malignant and normal cells in vitro as well as the effect on NAD homeostasis (NAD(+), NADH, and NMN levels), NAMPT inhibition and mitochondrial functionality were studied. The interactions of positively charged isoselenazolium salts with the negatively charged mitochondrial membrane model were assessed. Depending on the molecular structure, fused isoselenazolium salts display nanomolar to high micromolar cytotoxicities against MCF-7 and 4T1 breast tumor cell lines. The studied compounds altered NMN, NAD(+), and NADH levels and the NAD(+)/NADH ratio. Mitochondrial functionality experiments showed that fused isoselenazolium salts inhibit pyruvate-dependent respiration but do not directly affect complex I of the electron transfer system. Moreover, the tested compounds induce an immediate dramatic increase in the production of reactive oxygen species. In addition, the isoselenazolothiazolium derivative selectively binds to cardiolipin in a liposomal model. Isoselenazolium salts may be a promising platform for the development of potent drug candidates for anticancer therapy that impact mitochondrial pyruvate-dependent metabolism in breast cancer cells.

Three groups of synthetic lipids are chosen for studies: (1) 1,4-dihydropyridines (1,4-DHPs) containing two cationic moieties and their analogues; (2) 3,4-dihydro-2(1 H )-pyridones containing a cationic moiety; and (3) acyclic, open-chain analogues, i.e., 2-amino-3-alkoxycarbonylalkylammonium derivatives. 1,4-DHPs possessing dodecyl alkyl chains in the ester groups in positions 3 and 5 and cationic nitrogen-containing groups in positions 2 and 6 have high cytotoxicity in cancer cells HT-1080 (human lung fibrosarcoma) and MH-22A (mouse hepatoma), but low cytotoxicity in the noncancerous NIH3T3 cells (mouse embryonic fibroblast). On the contrary, similar compounds having short (methyl, ethyl, or propoxyethyl) chains in the ester groups in positions 3 and 5 lack cytotoxicity in the cancer cells HT-1080 and MH-22A even at high doses. Inclusion of fluorine atoms in the alkyl chains in positions 3 and 5 of the DHP cycle decreases the cytotoxicity of the mentioned compounds. Structurally related dihydropyridones with a polar head group are substantially more toxic to normal and cancerous cells than the DHP analogues. Open-chain analogues of DHP lipids comprise the same conjugated aminovinylcarbonyl moiety and possess anticancer activity, but they also have high basal cytotoxicity. Electrochemical oxidation data demonstrate that oxidation potentials of selected compounds are in the range of 1.6–1.7 V for cationic 1,4-DHP, 2.0–2.4 V for cationic 3,4-dihydropyridones, and 1.2–1.5 V for 2-amino-3-alkoxycarbonylalkylammonium derivatives. Furthermore, the tested cationic 1,4-DHP amphiphiles possess antiradical activity. Molecular topological polar surface area values for the tested compounds were defined in accordance with the main fragments of compound structures. The determined log P values were highest for dodecyl ester groups in positions 3 and 5 of the 1,4-DHP and lowest for short alkyl chain-containing amphiphiles.

In this data file the synthetic procedures for preparation of the original 4-pyridinium-1,4-dihydropyridines (4-Py-1,4-DHP) and their parent compounds – dialkyl 2,6-dimethyl-4-(3-pyridyl)-1,4-dihydropyridine-3,5-dicarboxylates were described. In total, 5 unpublished compounds were obtained and characterised. All the structures of original compounds were confirmed by Nuclear Magnetic Resonance (NMR, including 1H NMR and 13C NMR) and low resolution mass spectra (MS) data. Additionally, the cytotoxic properties of four 4-Py-1,4-DHPs were evaluated on 3 cell lines – normal NIH3T3 (mouse embryonic fibroblast), cancerous HT-1080 (human lung fibrosarcoma) and MH-22A (mouse hepatoma) and self-assembling properties were studied and characterisation of formed nanoparticles were performed using dynamic light scattering technique. In this article provided data are directly related to the previously published research articles – “Novel cationic amphiphilic 1,4-dihydropyridine derivatives for DNA delivery” [1] where compound 5 was tested as gene delivery agent without full physico-chemical characterisation and “Synthesis and studies of calcium channel blocking and antioxidant activities of novel 4-pyridinium and/or N-propargyl substituted 1,4-dihydropyridine derivatives” [2] where synthesis and physico-chemical characterisation as well as calcium channel blocking and antioxidant activities were described for compound 6. Synthesis of other compounds – parent 1,4-DHPs 1 and 2, and 4-Py-1,4-DHPs 3–5, their characterisation, estimation of cytotoxicity and self-assembling properties for all 4-Py-1,4-DHPs 3–6 are reported herein for the first time. Information provided in this data file can be used in medicinal chemistry by other scientists to estimate structure-activity relationships for the analysis and construction of various cationic 1,4-dihydropyridine derivatives and related heterocycles.

Substituted 6-aroylmethylsulfinyl-1,4-dihydropyridines 3 bearing methoxy-(chloro)phenyl groups at different positions of the ring have been prepared by a selective oxidation of sulfur atom of 6-aroylmethylsulfanyl-1,4-dihydropyridines 2 with oxone. Many oxidizing agents (oxone, m-chloroperoxybenzoic acid, cumylhydroperoxide and t-butyl hydroperoxide, Ti(Oi-Pr)(4)/(R,R)-DET)) were tested and oxone (mixture of salts 2KHSO(5)center dot KHSO4 center dot K2SO4)was found the most promising. 6-Aroylmethylsulfinyl-1,4-dihydropyridine 3c bearing trimethoxyphenyl group at positions 4 has revealed pronounced multidrug resistancemodulating (P-glycoprotein inhibition) activity exceeding that of the corresponding 6-aroylmethylsulfanyl-1,4-dihydropyridine 2c andverapamil.

The general aim of the current research is to find novel non-toxic small molecules with antimetastatic activity.

The design of nanoparticle delivery materials possessing biological activities is an attractive strategy for the development of various therapies. In this study, 11 cationic amphiphilic 4-(N-alkylpyridinium)-1,4-dihydropyridine (1,4-DHP) derivatives differing in alkyl chain length and propargyl moiety/ties number and position were selected for the study of their self-assembling properties, evaluation of their cytotoxicity in vitro and toxicity on microorganisms, and the characterisation of their interaction with phospholipids. These lipid-like 1,4-DHPs have been earlier proposed as promising nanocarriers for DNA delivery. We have revealed that the mean diameter of freshly prepared nanoparticles varied from 58 to 513 nm, depending upon the 4-(N-alkylpyridinium)-1,4-DHP structure. Additionally, we have confirmed that only nanoparticles formed by 4-(N-dodecylpyridinium)-1,4-DHP derivatives 3 and 6, and by 4-(N-hexadecylpyridinium)-1,4-DHP derivatives 10 and 11 were stable after two weeks of storage. The nanoparticles of these compounds were found to be homogenous in size distribution, ranging from 124 to 221 nm. The polydispersity index (PDI) values of 1,4-DHPs samples 3, 6, 10, and 11 were in the range of 0.10 to 0.37. We also demonstrated that the nanoparticles formed by 4-(N-dodecylpyridinium)-1,4-DHP derivatives 3, 6, and 9, and 4-(N-hexadecylpyridinium)-1,4-DHP derivatives 10 and 11 had zeta-potentials from +26.07 mV (compound 6) to +62.80 mV (compound 11), indicating a strongly positive surface charge and confirming the relative electrostatic stability of these nanoparticle solutions. Transmission electron microscopy (TEM) images of nanoaggregates formed by 1,4-DHPs 3 and 11 confirmed liposome-like structures with diameters around 70 to 170 nm. The critical aggregation concentration (CAC) value interval for 4-(N-alkylpyridinium)-1,4-DHP was from 7.6 µM (compound 11) to 43.3 µM (compound 6). The tested 4-(N-alkylpyridinium)-1,4-DHP derivatives were able to quench the fluorescence of the binary 1,6-diphenyl-1,3,5-hexatriene (DPH)—1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) system, demonstrating hydrophobic interactions of 1,4-DHPs with phospholipids. Thus, 4-(N-dodecylpyridinium)-1,4-DHP derivative 3 quenched the fluorescence of the DPH–DPPC system more efficiently than the other 4-(N-alkylpyridinium)-1,4-DHP derivatives. Likewise the compound 3, also 4-(N-dodecylpyridinium)-1,4-DHP derivative 9 interacted with the phospholipids. Moreover, we have established that increasing the length of the alkyl chain at the quaternised nitrogen of the 4-(N-alkylpyridinium)-1,4-DHP molecule or the introduction of propargyl moieties in the 1,4-DHP molecule significantly influences the cytotoxicity on HT-1080 (human fibrosarcoma) and MH-22A (mouse hepatocarcinoma) cell lines, as well as the estimated basal cytotoxicity. Additionally, it was demonstrated that the toxicity of the 4-(N-alkylpyridinium)-1,4-DHP derivatives on the Gram-positive and Gram-negative bacteria species and eukaryotic microorganism depended on the presence of the alkyl chain length at the N-alkyl pyridinium moiety, as well as the number of propargyl groups. These lipid-like compounds may be proposed for the further development of drug formulations to be used in cancer treatment.

Synthesis and cytotoxic studies of cyclohexanediones and 2-oxa-6-azabicyclo[2.2.2]octanes obtained in reaction of fluorinated 2,6-hetanediones with amines and ammonia respectively.

Complex, focused anticancer therapy approach has been developed in the Latvian Institute of Organic Synthesis by making use of privileged partially hydrogenated nitrogen-containing heterocycles, namely dihydropyridines, dihydropyrimidines, their oxidized heteroaromatic derivatives. Topics of research include: 1. Conventional approach by chemotherapy and synergism of anticancer drugs [1]; 2. Inhibition of multidrug resistance by inhibition of drug efflux pumps [2]; 3. Mitigation of cancer risk factors – e.g., hepatitis B virus chemotherapy for prevention of chronic liver diseases, because chronic hepatitis, in up to 40% of cases, progresses to cyrrhosis and further to hepatocellular carcinoma [3]; 4. Improvement of efficacy of cancer radiotherapy by use of radioprotectors to prevent damage of normal tissues. So, radioprotector diethone (dietone) for skin protection was discovered, elaborated, and developed as ointment. Compounds for protection of eyes, mucous tissues, salivary glands etc have been synthesized. Toxicity of dietone and novel radioprotectors is very low; 5.Amphiphilic compounds have been synthesized, nanoparticles for anticancer drug and gene delivery have been created, pleiotropic properties have been checked, inclusion of magnetic particles for targeted transport performed [4]. Acknowledgements The research was partially supported by the Latvian State Program Biomedicine. References 1.Bisenieks E., Duburs G. et al., Pharmaceutical combination of 5-fluorouracil and derivatives of 1,4-dihydropyridine. US 8492413B2, 2013. 2.Krauze A., Grinberga S. et al., Thieno[2,3-b]pyridines – a new class of multidrug resistance (MDR) modulators. Bioorg.Med.Chem. 2014, 22 (21), 5860-5870. 3.Sipola A., Dubova U., et al., Synthesis and evaluation of 1,4-dihydropyrimidine derivatives – hepatitis B virus capsid self-assembly inhibitors. EFMC International Symposium on Medicinal Chemistry. Ljubljana, Slovenia, 2018, P176. 4.Pajuste K. et al., Gene delivery agents possessing antiradical activity: Self-assembling cationic amphiphilic 1,4-dihydropyridine derivatives. New J.Chem. 2013, 37 (10), 3062-3075.

Aims and Objectives: The aim of the research is to obtain and to investigate the cytotoxicity of a novel class of non-toxic oximes – derivatives of N-(benzo[4,5]imidazo[2,1-b]thiazol-3-ylmethoxy)-ω- (hetarylsulfanyl)-alkanamidines. Materials and Methods: To assess the possible toxicity of the compounds, acute oral LD50 was calculated. The calculations were based on tested compounds IC50 values in relation to 3T3 (mouse fibroblast cell line) using NRU assay. Monolayer tumor cell lines HT-1080 (human fibrosarcoma, ATCC® CCL-121™), MH-22A (mouse hepatoma, ECACC code, 96121721) and NIH/3T3 (mouse Swiss Albino embryo fibroblasts, ATCC® CRL-1658™), were cultured in standard medium (Dulbecco`s modified Eagle`s medium) supplemented with 10% fetal bovine serum (“Sigma”). Results: E-Stereoselective synthesis of novel N-(benzo[4,5]imidazo[2,1-b]thiazol-3-ylmethoxy)-ω- (hetarylsulfanyl)alkanamidines as potential cytotoxic agents was carried out in three steps from corresponding thiones. N-(Benzo[4,5]imidazo[2,1-b]thiazol-3-ylmethoxy)-5-(benzothiazol-2-ylsulfanyl)-pentanamidine exhibits high activity in vitro on the monolayer tumour cell lines: MG-22A (mouse hepatoma) and HT-1080 (human fibrosarcoma). Besides this, the above compound exhibits low toxicity on the 3T3 cell line and low estimated acute oral LD50 (LD50 2759 mg/kg). Conclusion: In conclusion, such dramatic decreasing of expected acute toxicity and high cytotoxicity by the introduction of benzo[4,5]imidazo[2,1-b]thiazolyl fragment into N-hydroxy-ω-(hetarylsulfanyl)alkanamidines were demonstrated for the first time (see, for example, toxicity and cytotoxicity of compound 8b and corresponding unsubstituted oxime).