Trimeric and Tetrameric Cationic Styryl Dyes as Novel Fluorescence and CD Probes for ds-DNA and ds-RNA.

The wide use of mono- or bis-styryl fluorophores in biomedical applications prompted the presented design and study of a series of trimeric and tetrameric homo-analogues, styryl moieties arranged around a central aromatic core. The interactions with the most common biorelevant targets, ds-DNA and ds-RNA, were studied by a set of spectrophotometric methods (UV-VIS, fluorescence, circular dichroism, thermal denaturation). All studied dyes showed strong light absorption in the 350-420 nm range and strongly Stokes-shifted (+100-160 nm) emission with quantum yields (Φf) up to 0.57, whereby the mentioned properties were finely tuned by the type of the terminal cationic substituent and number of styryl components (tetramers being red-shifted in respect to trimers). All studied dyes strongly interacted with ds-DNA and ds-RNA with 1-10 nM-1 affinity, with dye emission being strongly quenched. The tetrameric analogues did not show any particular selectivity between ds-DNA or ds-RNA due to large size and consequent partial, non-selective insertion into DNA/RNA grooves. However, smaller trimeric styryl series showed size-dependent selective stabilization of ds-DNA vs. ds-RNA against thermal denaturation and highly selective or even specific recognition of several particular ds-DNA or ds-RNA structures by induced circular dichroism (ICD) bands. The chiral (ICD) selectivity was controlled by the size of a terminal cationic substituent. All dyes entered efficiently live human cells with negligible cytotoxic activity. Further prospects in the transfer of ICD-based selectivity into fluorescence-chiral methods (FDCD and CPL) is proposed, along with the development of new analogues with red-shifted absorbance properties.

Discovery of harmiprims, harmine-primaquine hybrids, as potent and selective anticancer and antimalarial compounds.

Although cancer and malaria are not etiologically nor pathophysiologically connected, due to their similarities successful repurposing of antimalarial drugs for cancer and vice-versa is known and used in clinical settings and drug research and discovery. With the growing resistance of cancer cells and Plasmodium to the known drugs, there is an urgent need to discover new chemotypes and enrich anticancer and antimalarial drug portfolios. In this paper, we present the design and synthesis of harmiprims, hybrids composed of harmine, an alkaloid of the ß-carboline type bearing anticancer and antiplasmodial activities, and primaquine, 8-aminoquinoline antimalarial drug with low antiproliferative activity, covalently bound via triazole or urea. Evaluation of their antiproliferative activities in vitro revealed that N-9 substituted triazole-type harmiprime was the most selective compound against MCF-7, whereas C1-substituted ureido-type hybrid was the most active compound against all cell lines tested. On the other hand, dimeric harmiprime was not toxic at all. Although spectrophotometric studies and thermal denaturation experiments indicated binding of harmiprims to the ds-DNA groove, cell localization showed that harmiprims do not enter cell nucleus nor mitochondria, thus no inhibition of DNA-related processes can be expected. Cell cycle analysis revealed that C1-substituted ureido-type hybrid induced a G1 arrest and reduced the number of cells in the S phase after 24 h, persisting at 48 h, albeit with a less significant increase in G1, possibly due to adaptive cellular responses. In contrast, N-9 substituted triazole-type harmiprime exhibited less pronounced effects on the cell cycle, particularly after 48 h, which is consistent with its moderate activity against the MCF-7 cell line. On the other hand, screening of their antiplasmodial activities against the erythrocytic, hepatic, and gametocytic stages of the Plasmodium life cycle showed that dimeric harmiprime exerts powerful triple-stage antiplasmodial activity, while computational analysis showed its binding within the ATP binding site of PfHsp90.