X-ray, spectroscopic and semiempirical investigation of the structure of lasalocid 6-bromohexyl ester and its complexes with alkali metal cations

Synthesis of Lasalocid-Based Bioconjugates and Evaluation of Their Anticancer Activity

Using rationally designed bioconjugates is an attractive strategy to develop novel anticancer drugs with enhanced therapeutic potential and minimal side effects compared to the native structures. With respect to the promising activity of lasalocid (LAS) toward various cancer cells, this polyether ionophore seems to be an ideal candidate for bioconjugation. Herein, we describe the synthetic access to a cohort of nine conjugated products of LAS, in which the ionophore biomolecule was successfully combined via covalent bonds with selected anticancer therapeutics or other anticancer active components. The in vitro screening of a series of cancer cell lines allowed us to identify three products with improved anticancer activity profiles compared to those of the starting materials. The results indicate that human prostate cancer cells (PC3) and human primary colon cancer cells (SW480) were essentially more sensitive to exposure to LAS derivatives than human keratinocytes (HaCaT). Furthermore, the selected products were stronger inducers of late apoptosis and/or necrosis in PC3 and SW480 cancer cells, when compared to the metastatic variant of colon cancer cells (SW620). To establish the anticancer mechanism of LAS-based bioconjugates, the levels of interleukin 6 (IL-6) and reactive oxygen species (ROS) were measured; the tested compounds significantly reduced the release of IL-6, while the level of ROS was significantly higher in all the cell lines studied.

Structures and properties of naturally occurring polyether antibiotics

Polyether ionophores represent a large group of natural, biologically active substances produced by Streptomyces spp. They are lipid soluble and able to transport metal cations across cell membranes. Several of polyether ionophores are widely used as growth promoters in veterinary. Polyether antibiotics show a broad spectrum of bioactivity ranging from antibacterial, antifungal, antiparasitic, antiviral, and tumour cell cytotoxicity. Recently, it has been shown that some of these compounds are able to selectively kill cancer stem cells and multidrug-resistant cancer cells. Thus, they are recognized as new potential anticancer drugs. The biological activity of polyether ionophores is strictly connected with their molecular structure; therefore, the purpose of this paper is to present an overview of their formula, molecular structure, and properties.

Synthesis, FT-IR, ¹H, ¹³CNMR, ESI MS and PM5 studies of a new Mannich base of polyether antibiotic - Lasalocid acid and its complexes with Li⁺, Na⁺ and K⁺ cations

The polyether antibiotic Lasalocid acid has been converted to its Mannich base derivative by a chemoselective one-pot reaction with formaldehyde and morpholine through the decarboxylation process. Spectroscopic studies of the structure of this new derivative have shown that in this ortho-phenol Mannich base the O-H⋯N intarmolecular hydrogen bond is present. The compound forms complexes with Li(+), Na(+) and K(+) cations of exclusively 1:1 stoichiometry. The structures of these complexes have been studied and visualized by semi-empirical calculation based on results of spectrometric and spectroscopic investigation. It is demonstrated that in contrast to Lasalocid acid the novel Mannich type derivative forms preferential complexes with Li(+) cation.