Ewa Bębenek

Synthesis, structure and cytotoxic activity of new acetylenic derivatives of betulin.

A new series of betulin derivatives containing one or two pharmacophores bearing an acetylenic and carbonyl function at the C-3 and/or C-28 positions has been synthesized and characterized by 1H- and 13C-NMR, IR, MS and elemental analyses. The crystal structure of 28-O-propynoylbetulin was determined by X-ray structural analysis. All new compounds, as well as betulin, were tested in vitro for their antiproliferative activity against human SW707 colorectal, CCRF/CEM leukemia, T47D breast cancer, and against murine P388 leukemia and Balb3T3 normal fibroblasts cell lines. Most of the compounds showed better cytotoxicity than betulin and cisplatin used as reference agent. 28-O-Propynoylbetulin was the most potent derivative, being over 500 times more potent than betulin and about 100 times more cytotoxic than cisplatin against the human leukemia (CCRF/CEM) cell line, with an ID50 value of 0.02 μg/mL.

Influence of betulin and 28-O-propynoylbetulin on proliferation and apoptosis of human melanoma cells (G-361).

INTRODUCTION Pentacyclic triterpenes are a group of compounds known to have anticancer activity. One of the best characterized triterpenes is betulin, which can be isolated from bark of birch trees and modified into new compounds with various interesting medical properties. Betulin is involved in activation of the caspase cascade and promotes cell death. The aim of the study was to investigate the effect of betulin and its acetylenic derivative, 28-O-propynoylbetulin, on proliferation and apoptosis in a human melanoma cell line. MATERIALS AND METHODS The G-361 melanoma cell line was used. To evaluate growth arrest and caspase-3 activity, cells were treated with betulin and its derivative at a wide range of concentrations from 0.1 to 10 μg/mL. RESULTS Betulin and 28-O-propynoylbetulin inhibited cell proliferation in a concentration-dependent manner. The cell cycle analysis revealed an increase of the sub-G1 cell fraction (representing dead cells) after incubation of cells with betulin and 28-O-propynoylbetulin. The observed cytotoxic effects were more pronounced for 28-O-propynoylbetulin. Activity of caspase-3 in 28-O-propynoylbetulin treated cells was nearly 2-fold greater compared to cells incubated with betulin. DISCUSSION Our results show that betulin and 28-O-propynoylbetulin were effective in inhibition of cell growth and induction of apoptosis in a human melanoma cell line. The addition of the propynoyl group at the C-28 hydroxyl group of betulin led to a greater proapoptotic and antiproliferative effect in comparison to unmodified betulin. These observations suggest that the obtained derivative is a potent anti-melanoma agent.

Crystal structure of betulinic acid-DMSO solvate

Abstract The crystal structure of betulinic acid-DMSO (1:1) solvate has been determined. The betulinic acid, [3β-hydroxy-lup-20(29)-en-28-oic acid, C30H48O3] is considered as a promising natural agent for the clinical treatment for various types of cancer. Crystals of betulinic acid for X-ray structural analysis were grown from a DMSO-water (9:1, v/v) solution. Betulinic acid-DMSO (1:1) solvate crystallizes in the orthorhombic symmetry the P212121 space group, Z = 4. The unit cell parameters are as follows: cell lengths a = 6.9417(2) Å, b = 13.8559(5) Å, c = 31.6232(10) Å, V = 3041.63(17) Å3. Betulinic acid molecules are hydrogen bonded to DMSO molecules. The weak intermolecular hydrogen bonds and van der Waals interactions are present in the crystal structure. The crystal and molecular structures of betulinic acid-DMSO solvates are discussed with reference to betulin and betulinic acid derivatives.

X-Ray Diffraction and Infrared Spectroscopy of N,N- Dimethylformamide and Dimethyl Sulfoxide Solvatomorphs of Betulonic Acid

X-ray diffraction and infrared spectroscopy measurements for the N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvatomorphs of betulonic acid (BA) were investigated. BA [3-oxolup-20(29)-en-28-oic acid, C(30)H(46)O(3)] exhibits a wide spectrum of biological activities and is considered to be a promising natural agent for the treatment of various cancer diseases. BA as a noncrystalline substance was obtained by oxidation of betulin. Crystal structures and the spectral data allowed analysis of hydrogen bonding (H-bonding), molecular conformation, and crystal packing differences in the solvatomorphs. Crystals of BA solvates were grown from the DMF-acetone (1:10, v/v) and DMSO-water (9:1, v/v) solutions. BA-DMF (1:1) solvate crystallizes in the monoclinic P2(1) space group, Z = 2. The unit cell parameters are as follows: cell lengths a = 13.2458(5) Å, b = 6.6501(2) Å, c = 17.9766(7) Å, and β = 110.513(4)°. BA-DMSO (1:1) solvate crystallizes in the orthorhombic P2(1)2(1)2(1) (Z = 4) space group with the following unit cell parameters: a = 6.6484(4) Å, b = 13.3279(8) Å, and c = 32.6821(19) Å. Conformational analysis of the six-membered rings, cyclopentane ring, and isopropenyl group showed differences in comparison with other betulin derivatives examined earlier. For both solvates, the intermolecular packing arrangement was governed mainly by H-bonds. The shortest H-bonds with D···A distances of 2.604 and 2.657 Å, and almost linear DH···A connection occurred between OH of carboxylic group of BA and oxygen atoms from O=C and O=S groups of DMF and DMSO, respectively.

Betulin Phosphonates; Synthesis, Structure, and Cytotoxic Activity

Betulin derivatives are a widely studied group of compounds of natural origin due to their wide spectrum of biological activities. This paper describes new betulin derivatives, containing a phosphonate group. The allyl-vinyl isomerization and synthesis of acetylenic derivatives have been reported. Structural identification of products as E and Z isomers has been carried out using 1H-, 13C-, 31P-NMR, and crystallographic analysis. The crystal structure in the orthorhombic space group and analysis of crystal packing contacts for 29-diethoxyphosphoryl-28-cyclopropylpropynoyloxy-lup-20E(29)-en-3β-ol 8a are reported. All new compounds were tested in vitro for their antiproliferative activity against human T47D (breast cancer), SNB-19 (glioblastoma), and C32 (melanoma) cell lines.

Synthesis, Structure and Cytotoxic Activity of Mono- and Dialkoxy Derivatives of 5,8-Quinolinedione.

A series of 5,8-quinolinedione derivatives containing one or two alkoxy groups was synthesized and characterized by 1H- and 13C-NMR, IR and MS spectra. X-ray diffraction was used to investigate the crystal structures of 6-chloro-7-(2-cyjanoethoxy)-5,8-quinolinedione and 6,7-di(2,2,2-trifloroethoxy)-5,8-quinolinedione. All studied compounds were tested in vitro for their antiproliferative activity against three human cancer cell lines and human normal fibroblasts. Most of the compounds showed higher cytotoxicity than the starting compound, 6,7-dichloro-5,8-quinolinedione, and cisplatin, which was used as a reference agent.

Novel Triazole Hybrids of Betulin: Synthesis and Biological Activity Profile

Betulin derivatives containing a 1,2,3-triazole ring possess a wide spectrum of biological activities, including antiviral, anticancer, and antibacterial activity. A series of novel triazoles were prepared by the 1,3-dipolar cycloaddition reaction between the alkyne derivatives of betulin and organic azides. The chemical structures of the obtained compounds were defined by 1H and 13C NMR, IR, and high-resolution mass spectrometry (HR-MS) analysis. The target triazoles were screened for their antiviral activity against DNA and RNA viruses. The cytotoxic activity of the obtained compounds 5a–k and 6a–h was determined using five human cancer cell lines (T47D, MCF-7, SNB-19, Colo-829, and C-32) by a WST-1 assay. The bistriazole 6b displayed a promising IC50 value (0.05 μM) against the human ductal carcinoma T47D (500-fold higher potency than cisplatin). The microdilution method was applied for an evaluation of the antimicrobial activity of all of the compounds. The triazole 5e containing a 3′-deoxythymidine-5′-yl moiety exhibited antibacterial activity against two gram-negative bacteria vz. Klebsiella pneumoniae and Escherichia coli (minimal inhibitory concentration (MIC) range of 0.95–1.95 μM).

Structural determinants influencing halogen bonding: a case study on azinesulfonamide analogs of aripiprazole as 5-HT 1A , 5-HT 7 , and D 2 receptor ligands

A series of azinesulfonamide derivatives of long-chain arylpiperazines with variable-length alkylene spacers between sulfonamide and 4-arylpiperazine moiety is designed, synthesized, and biologically evaluated. In vitro methods are used to determine their affinity for serotonin 5-HT1A, 5-HT6, 5-HT7, and dopamine D2 receptors. X-ray analysis, two-dimensional NMR conformational studies, and docking into the 5-HT1A and 5-HT7 receptor models are then conducted to investigate the conformational preferences of selected serotonin receptor ligands in different environments. The bent conformation of tetramethylene derivatives is found in a solid state, in dimethyl sulfoxide, and as a global energy minimum during conformational analysis in a simulated water environment. Furthermore, ligand geometry in top-scored complexes is also bent, with one torsion angle in the spacer (τ2) in synclinal conformation. Molecular docking studies indicate the role of halogen bonding in complexes of the most potent ligands and target receptors.

Application of thin-layer chromatography to evaluate the lipophilicity of 5,8-quinolinedione compounds

Lipophilicity is a very important property while designing new drugs. Its influence on the pharmacological responses of compounds has been known since the 19th century. Also, many researchers try to find the relationships between structure and activity of newly synthetized compounds. The aim of this study was to determine the lipophilicity of 5,8-quinolinedione derivatives using thin-layer chromatography. Moreover, the structure—activity correlation between experimental and theoretical parameters of lipophilicity and anticancer activity was described. A series of 18 compounds was investigated. Experimental lipophilicity was determined by use of reversed-phase thin-layer chromatography (RP-TLC) using RP-18 F254s plates impregnated with silicone oil and the mixture of acetone and water solution of buffer Tris (pH = 7.4) in different volume compositions as mobile phases. Values of calculated lipophilicity (ALOGPs, AClogP, miLogP, KOWWIN, XLOGP2, MLogP, ABlogP, and ACD/LogP) were taken from the internet database. The correlation between experimental and calculated values of lipophilicity was found. For some compounds investigated, the calculated values of lipophilicity were relatively high. The correlation coefficient for these relationships was not very high but statistically significant. It confirms that the structure of compounds investigated affects the value of lipophilicity. The correlation between lipophilicity and anticancer activity was also determined, but unfortunately, no correlation was found. Additionally, similarity analysis was prepared for compounds investigated and results of lipophilicity were obtained.