Cytotoxic Potential of a-Azepano- and 3-Amino-3,4-SeCo-Triterpenoids

Semi-synthetic triterpenoids, holding an amino substituted seven-membered A-ring (azepano-ring), which could be synthesized from triterpenic oximes through a Beckmann type rearrangement followed by a reduction of lactame fragment, are considered to be novel promising agents exhibiting anti-microbial, alpha-glucosidase, and butyrylcholinesterase inhibitory activities. In this study, in an attempt to develop new antitumor candidates, a series of A-ring azepano- and 3-amino-3,4-seco-derivatives of betulin, oleanolic, ursolic, and glycyrrhetinic acids were evaluated for their cytotoxic activity against five human cancer cell lines and non-malignant mouse fibroblasts by means of a colorimetric sulforhodamine assay. Azepanoallobetulinic acid amide derivative 11 was the most cytotoxic compound of this series but showed little selectivity between the different human tumor cell lines. Flow cytometry experiments showed compound 11 to act mainly by apoptosis (44.3%) and late apoptosis (21.4%). The compounds were further screened at the National Cancer Institute towards a panel of 60 cancer cell lines. It was found that compounds 3, 4, 7, 8, 9, 11, 15, 16, 19, and 20 showed growth inhibitory (GI₅₀) against the most sensitive cell lines at submicromolar concentrations (0.20–0.94 μM), and their cytotoxic activity (LC₅₀) was also high (1–6 μM). Derivatives 3, 8, 11, 15, and 16 demonstrated a certain selectivity profile at GI₅₀ level from 5.16 to 9.56 towards K-562, CCRF-CEM, HL-60(TB), and RPMI-8226 (Leukemia), HT29 (Colon cancer), and OVCAR-4 (Ovarian cancer) cell lines. Selectivity indexes of azepanoerythrodiol 3 at TGI level ranged from 5.93 (CNS cancer cell lines SF-539, SNB-19 and SNB-75) to 14.89 for HCT-116 (colon cancer) with SI 9.56 at GI₅₀ level for the leukemia cell line K-562. The present study highlighted the importance of A-azepano-ring in the triterpenic core for the development of novel antitumor agents, and a future aim to increase the selectivity profile will thus lie in the area of modifications of azepano-triterpenic acids at their carboxyl group.     

Study of the Spatial and Current Dynamics of Optical Loss in Semiconductor Laser Heterostructures by Optical Probing

Semiconductors - The spatial and temporal dynamics of the optical loss and carrier density in the heterostructure of a semiconductor laser with a segmented contact are studied using an optical...     

Multilevel Recording in Ge2Sb2Te5 Thin Films

Semiconductors - The current–voltage characteristics measured on Ge2Sb2Te5 thin films in the current mode are studied. The effect of multilevel recording is established when applying...     

Determining the Solubility of RaF2 in Water

Radiochemistry - The solubility of radium fluoride in water was determined. Radium was purified by the chromatographic method with a BioRad AG-50×8 (NH4+) sorbent (200–400 mesh). The...     

Three-Dimensional Numerical Simulation of the Development of Instability of a Contact Boundary of Colliding Metal Plates within the Gas-Dynamic Approximation

High Temperature - The development of the initial stage of instability of a contact boundary of colliding metal plates has been numerically simulated. The mathematical model is based on the Euler...     

Growth and properties of isoparametric InAlGaPAs/GaAs heterostructures

The results obtained in the growth of isoparametric InAlGaPAs/GaAs heterostructures are discussed. The composition, structural quality, and luminescence properties of the heterostructures are studied.     

Water Affinity to Epitaxial Graphene: The Impact of Layer Thickness

The sensitivity to water vapour of one‐, two‐, and three‐layer epitaxial graphene (1, 2, and 3LG) is examined in this study. It is unambiguously shown that graphene's response to water, as measured by changes in work function and carrier density, is dependent on its thickness, with 1LG being the most sensitive to water adsorption and environmental concentration changes. This is furthermore substantiated by surface adhesion measurements, which bring evidence that 1LG is less hydrophobic than 2LG. Yet, surprisingly, it is found that other contaminants commonly present in ambient air have a greater impact on graphene response than water vapor alone. This study indicates that graphene sensor design and calibration to minimize or discriminate the effect of the ambient, in which it is intended to operate, are necessary to insure the desired sensitivity and reliability of sensors. The present work will aid in developing models for realistic graphene sensors and establishing protocols for molecular sensor design and development.     

Phosphorus-containing compounds of pollucite structure and radiochemical problems

New pollucite-like phosphorus-containing compounds with cesium and uni-, bi-, and trivalent cations (Li; Mg, Mn, Co, Ni, Cu, Zn, Cd, Sr, Ba; Al, Cr, Fe), many of which can be present in various combinations in wastes from radiochemical processes, were synthesized. The individual phases obtained were characterized by X-ray phase analysis and IR spectroscopy. The symmetry of the unit cells of the phosphorus-containing compounds decreases relative to the silicon analog (pollucite natural mineral) from Ia3d to I4₁32. The behavior of the compounds on heating to 1000°C, under hydrothermal conditions at 90°C, in aqueous systems (distilled water and seawater) at 25°C, and in a CsCl melt at 680°C was studied. The chemical and phase composition of the samples remained unchanged under all these conditions. The Cs leaching rates varied from 7.1 × 10⁻⁶ to 1.46 × 10⁻⁵ g cm⁻² day⁻¹. The “crystal-chemical modeling” of the new possible compositions of the compounds with the expected pollucite structure was performed.