Ana R.R.P. Almeida

The in vitro anticancer activity of the crude extract of the sponge-associated fungus Eurotium cristatum and its secondary metabolites

Background: Marine natural products has captivated many researchers over the years and there is always a need for sources of diverse and pharmacologically active leads in the area of anticancer drugs. Materials and Methods: The ethyl acetate extract of the fungus Eurotium cristatum (ECE), isolated from the marine sponge Mycale sp., furnished 2-(2’, 3-epoxy-1’,3’-heptadienyl)-6-hydroxy-5-(3-methyl-2-butenyl) benzaldehyde (1), 1,8-dihydroxy-6-methoxy-3-methyl-9,10-anthracenedione (physcion, 2), and the dioxopiperazine alkaloid echinulin (3). The structures of the compounds were established by Nuclear Magnetic Resonance (NMR) spectral analysis (1H, 13C, DEPT, COSY, HSQC, and HMBC). The ECE and its metabolites were evaluated for their growth inhibitory activity on the following three human tumor cell lines: breast adenocarcinoma (MCF-7), non-small lung cancer (NCI-H460), and melanoma (A375-C5). Results: The results showed that the ECE was active in all the three cell lines, with the values of GI50 = 44.3 ± 1.2, 45.5 ± 7.5, and 71.3 ± 2.1 μg/ml for MCF-7, NCI-H460, and A375-C5, respectively. Compound 1 also exhibited moderate growth inhibitory activity against all the three cell lines (GI50 = 58.3 ± 1.2, 46.0 ± 5.5, and 116.7 ± 7.2 μM for MCF-7, NCI-H460, and A375-C5, respectively), whereas compound 3 showed only weak inhibition against MCF-7 (GI50 = 109.7 ± 0.3 μM) and NCI-H460 (GI50 = 96.7 ± 1.5 μM) but was inactive against A375-C5 (GI50 >150 μM). On the contrary, compound 2 was inactive in all the three cell lines at the highest concentration tested (150 μM). Furthermore, ECE was investigated for its effect on the cell cycle in the NCI-H460 cells. Analysis of the cell cycle profile showed that ECE was able to cause a slight cell arrest in the G1 phase, with a corresponding decrease of cells in the S and G2/M phases. Conclusion: The secondary metabolites isolated [Compound 1] from the crude ethyl acetate extract of the culture of the marine fungus E. cristatum were found as the most potent compound regarding cell growth inhibition.

A new approach for the estimation of sublimation enthalpies and vapor pressures of crystalline benzene derivatives

This work presents a new approach for estimating sublimation enthalpies and vapor pressures of substituted benzenes. Proposed estimating equations were based on a collection of selected literature results of vapor pressures of ca. 240 benzene derivatives attached with 30 different substituents. Compared to experimental results, best estimates are obtained from the equations that include the temperature of fusion. A review of the results determined for substituted benzenes using two different calorimetric techniques shows that the results of enthalpies of sublimation derived from vapor pressures seem to be more reliable than those derived from the calorimetric techniques.

Enantiomeric resolution of albendazole sulfoxide by semipreparative HPLC and in vitro study of growth inhibitory effects on human cancer cell lines

Analytical and semipreparative high performance liquid chromatography methods using polysaccharide-based chiral stationary phases were developed for the enantiomeric resolution of albendazol sulfoxide. The enantioseparation of this compound was evaluated with four chiral stationary phases: cellulose and amylose tris(3,5-dimethylphenylcarbamate), amylose tris[(S)-1-phenylethylcarbamate] and amylose tris(3,5-dimethoxyphenylcarbamate), under three elution conditions: normal, reversed-phase and polar organic mode. The influences of the mobile phase and of the structure of the chiral stationary phase on the enantiomeric separation are discussed. The best chiral performances were achieved on an amylose tris(3,5-dimethylphenylcarbamate) phase under normal (R(s)=4.96) and polar organic mode (R(s)=2.60 and 3.09). A polar organic condition using methanol as mobile phase offered shorter retention factors (k(1)=0.34) and was scaled up to semipreparative HPLC to obtain milligram quantities of both albendazole sulfoxide enantiomers for further in vitro studies. Optical rotation and circular dichroism of both enantiomers of albendazole sulfoxide was determined. The compounds ABZ, ABZ-SO, (R)-(+)-ABZ-SO and (S)-(-)-ABZ-SO were all evaluated regarding their capacity to inhibit the in vitro growth of three human tumor cell lines: MCF-7 (breast adenocarcinoma), NCI-H460 (non-small cell lung cancer) and A375-C5 (melanoma). In addition, the effect of the (R)-(+)-ABZ-SO compound in the cell cycle profile and apoptosis of MCF-7 cells were also studied. Results indicated that compound ABZ was the most potent regarding cell growth inhibition and that the (+)-(R)-ABZ was a more potent inhibitor of cell growth than the (S)-(-)-ABZ-SO, particularly in the MCF-7 cell line. In addition, the (R)-(+)-ABZ-SO significantly increased the levels of apoptosis of the MCF-7 cells.

Thermodynamic study of sesamol, piperonyl alcohol, piperonylic acid and homopiperonylic acid: a combined experimental and theoretical investigation

The standard (p(o)= 0.1 MPa) molar energies of combustion in oxygen, at T= 298.15 K, of four 1,3-benzodioxole derivatives (sesamol, piperonyl alcohol, piperonylic acid and homopiperonylic acid) were measured by static bomb calorimetry. The values of the standard molar enthalpies of sublimation, at T= 298.15 K, were derived from vapour pressure-temperature measurements using the Knudsen effusion technique. Combining these results the standard molar enthalpies of formation of the compounds, in the gas phase, at T= 298.15 K, have been calculated: sesamol (-325.7 +/- 1.9) kJ mol(-1); piperonyl alcohol (-329.0 +/- 2.0) kJ mol(-1); piperonylic acid (-528.9 +/- 2.6) kJ mol(-1) and homopiperonylic acid (-544.5 +/- 2.9) kJ mol(-1). The most stable geometries of all the compounds were obtained using the density functional theory with the B3LYP functional and two basis sets: 6-31G** and 6-311G**. The nonplanarity of the molecules was analyzed in terms of the anomeric effect, which is believed to arise from the interaction between a nonbonded oxygen p orbital and the empty orbital sigma*(CO) involving the other oxygen atom. Calculations were performed to obtain estimates of the enthalpies of formation of all the benzodioxoles using appropriate isodesmic reactions. There is a perfect agreement between theoretical and experimental results.

Prediction of enthalpy and standard Gibbs energy of vaporization of haloaromatics from atomic properties.

Halogenated benzenes form a class of pollutants with a huge number of members - 1504 distinct benzene compounds, where one or more hydrogen atoms are replaced by halogens, may exist theoretically. This study presents a user friendly method for accurate prediction of vapor pressures and enthalpies of vaporization, at 298.15 K, of any mono or poly halobenzene compound. The derived equations for the prediction of those vaporization properties depend just on the number of each constituent halogen atom. This is a consequence of the absence of intramolecular interactions between the halogen atoms, revealed after examining vaporization results of ca. 40 halogenated benzenes. In order to rationalize the estimation equations, the contribution of the halogen atoms for the referred to above properties of vaporization was decomposed into two atomic properties - the volume and electron affinity. Extension of the applicability of the estimation method to substituted benzenes containing other substituent groups beyond halogen atoms as well as to some polycyclic aromatic species was tested with success.

A brief review of the methods used to evaluate vapour pressures and sublimation enthalpies

A brief review of the experimental methods used to evaluate vapour pressures and sublimation enthalpies is presented. The methods discussed have been used for determining the results of several substituted benzenes that were collected in a database, with the main purpose of developing new estimation methods of these thermodynamic properties. A critical evaluation of the two most used calorimetric techniques for determining enthalpies of sublimation is also addressed.