Structural and spectroscopic studies of a new 2-naphthylmethyl ester of lasalocid acid

Synthesis, X-ray studies and antiproliferative activity of novel lasalocid amides

Seeking new drug candidates among compounds of natural origin is an effective and widely used method of fighting various diseases, especially cancer. Lasalocid acid is one of the naturally occurring polyether ionophore antibiotics, which also exhibits interesting anticancer activity. Therefore, to expand the knowledge about the anticancer properties of lasalocid derivatives, a series of its new amides were synthesized and their antiproliferative activity against cancer cell lines was studied. Amides 7-9 with an aromatic substituent, displayed potent antiproliferative activity (IC50: 0.84-5.18 μM) and demonstrated a good selectivity index (SI: 1.4-15.3). Furthermore, almost all of lasalocid amides overcame the drug resistance of the doxorubicin-resistant cancer cell line (LoVo/DX). Because the biological activity of ionophores is strictly connected with their ability to transport the Na+ cation through lipid bilayers, the crystal structure of the complex of compound 8 with the Na+ cation was resolved. Lasalocid amides exhibit a pseudocyclic structure and are able to coordinate the Na+ cation.

Spectroscopic studies of the equilibrium between complexes of lasalocid acid with propargylamine and metal cations

The molecular structure of 1:1 complex formed between the naturally occurring polyether ionophore, called lasalocid acid (LAS) and propargylamine (PROP) is studied by X-ray, FT-IR, (1)H NMR, (13)C NMR and ESI-MS methods. The complex formed between deprotonated LAS acid and protonated PROP molecule is stabilized by intra- and inter-molecular hydrogen bonds. The protons of the protonated amine group are hydrogen bonded to etheric and hydroxyl oxygen atoms of the LAS anion. The similarity of the FT-IR spectra of the LAS-PROP complex in solid state and in solution demonstrated that the molecular structures of the complex in both states are comparable. It is shown that LAS in solution can form concurrent complexes with metal cations (M=Li(+), Na(+), K(+)) and amine existing in equilibrium. Analysis of the structures of lasalocid complexes is important for a better understanding of the antibacterial and anticancer properties of lasalocid acid.

Spectroscopic, crystallographic and theoretical studies of lasalocid complex with ammonia and benzylamine

A natural antibiotic--Lasalocid is able to form stable complexes with ammonia and organic amines. New complexes of lasalocid with benzylamine and ammonia were obtained in the crystal forms and studied using X-ray, FT-IR, (1)H NMR, (13)C NMR and DFT methods. These studies have shown that in both complexes the proton is transferred from the carboxylic group to the amine group with the formation of a pseudo-cyclic structure of lasalocid anion complexing the protonated amine or NH4(+) cation. The spectroscopic and DFT studies demonstrated that the structure of the complex formed between Lasalocid and benzylamine in the solid is also conserved in the solution and gas phase. In contrast, the structure of the complex formed between lasalocid and ammonium cation found in the solid state undergoes dissociation in chloroform solution accompanied with a change in the coordination form of the NH4(+) cation.

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.