Inclusion Of Polar Groups Research Articles

Evaluation of triterpenes derivatives in the viability of Leishmania amazonensis and Trichomonas vaginalis

Trichomonas vaginalis and Leishmania spp. are protozoal species responsible for millions of cases of parasitic diseases worldwide. Considering the potential of natural products and the need for more effective and less toxic alternatives to treat trichomoniasis and leishmaniasis, this study aimed to evaluate the effect of two series of triterpenes derivatives with different modifications at C-3 and C-28 positions of the ursolic acid (UA) and betulinic acid (BA) against trophozoites of Trichomonas vaginalis and promastigotes forms of Leishmania (L.) amazonensis. The compounds modified just at C-3 were the most active. The 3β-acetyl betulinic acid (1b) reduced the trophozoites viability of T. vaginalis at 74%, followed by the 3-oxo ursolic acid and 3-oxo betulinic acid (3a and 3b) compounds (55% of reduction). The compound 3β-isobutyl ursolic acid (7a) inhibited the viability of L. amazonensis promastigotes by 55%. Therefore, analyzing the structure-activity relationship and the data of literature, it is possible to suppose that the inclusion of polar groups in the skeletons could improve the antiprotozoal activity. Overall, further studies are necessary to develop triterpenic derivatives with more powerful trichomonicidal and leishmanicidal properties.

Effects of longitudinal quadrupoles on the phase behavior of a Gay–Berne fluid

The effects of longitudinal quadrupole moments on the formation of liquid crystalline phases are studied by means of constant NPT Monte Carlo simulation methods. The popular Gay–Berne model mesogen is used as the reference fluid, which displays the phase sequences isotropic-smectic A-smectic B and isotropic-smectic B at high (T*=2.0) and low (T*=1.5) temperatures, respectively. With increasing quadrupole magnitude the smectic phases are observed to be stabilized with respect to the isotropic liquid, while the smectic B is destabilized with respect to the smectic A. At the lower temperature, a sufficiently large quadrupole magnitude results in the injection of the smectic A phase into the phase sequence and the replacement of the smectic B phase by the tilted smectic J phase. The nematic phase is also injected into the phase sequence at both temperatures considered, and ultimately for sufficiently large quadrupole magnitudes no coherent layered structures were observed. The stabilization of the smectic A phase supports the commonly held belief that, while the inclusion of polar groups is not a prerequisite for the formation of the smectic A phase, quadrupolar interactions help to increase the temperature and pressure range for which the smectic A phase is observed. The quality of the layered structure is worsened with increasing quadrupole magnitude. This behavior, along with the injection of the nematic phase into the phase sequence, indicate that the general tendency of the quadrupolar interactions is to destabilize the layered structure. A pressure dependence upon the smectic layer spacing is observed. This behavior is in much closer agreement with experimental findings than has been observed previously for nonpolar Gay–Berne and hard spherocylinder models.

Studies on the role of protein synthesis and of sodium on the regulation of ornithine decarboxylase activity

The minimum requirements for eliciting or enhancing ornithine decarboxylase activity (EC. 4.1.1.17); L-ornithine carboxylase) in neuroblastoma cells incubated in salts-glucose solutions have been investigated. These incubation conditions permit the study of changes in ornithine decarboxylase activity independently of the growth-associated reactions that occur in cell culture media (Chen, K.Y. and Canellakis, E.S. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 3791–3795). Ornithine decarboxylase activity can be elicited by a variety of asparagine and other amino acid analogs, including α-aminoisobutyric acid, that cannot participate in protein synthesis. Of the eleven asparagine analogs tested. α-N- CH 3- DL-asparagine is the most potent in eliciting ornithine decarboxylase activity and is equivalent to asparagine in this regard. Inclusion of polar groups into the asparagine molecule results in the loss of its ability to elicit ornithine decarboxylase activity. With the use of these analogs and of analogs of other amino acids it is shown that the rapid fall in ornithine decarboxylase activity that is noted following cycloheximide treatment may not be a consequence of the inhibition of protein synthesis. The rapid fall in ornithine decarboxylase activity is primarily due to the removal of the agent that elicits and stabilizes its activity. These results, the finding that α-amminoisobutyric acid stimulates ornithine decarboxylase activity and that sodium is required for the stimulation of ornithine decarboxylase activity are discussed in relation to the ‘A’ amino acid transport system.