Biomedical subjects

Regina H A Santos

Publications and source records attributed to Regina H A Santos.

3 recordsLinked to original sources

PubMed2004

Activation of carbon dioxide by bicyclic amidines.

Activation of the carbon dioxide molecule was achieved using bicyclic amidines (DBU, PMDBD, and DBN). The solution reaction of CO(2) with amidines yielded the corresponding zwitterionic complexes through the formation of a N-CO(2) bond. (13)C NMR data confirmed the carbamic nature of the carbamic zwitterions, DBU-CO(2) and PMDBD-CO(2). However, when these adducts were crystallized, the X-ray analyses of the single crystals were in agreement with bisamidinium bicarbonate salt structures, indicating that structural changes occurred in the crystallization process. The elemental and thermogravimetric analysis data for the carbamic zwitterions, DBU-CO(2) and PMDBD-CO(2), initially obtained by the direct reaction of amidines with CO(2), suggest that these molecules are probably associated with one molecule of water by hydrogen-bond formation (amidinium(+)-COO(-)...H(2)O). A correlation was observed between the thermal stability and the transcarboxylating activity for the amidine-CO(2) complexes. Theoretical calculations of hardness were performed at the B3LYP/cc-pVTZ level of theory and showed concordance with the experimental reactivity of DBU and PMDBD toward CO(2).

Journal Article↗

PubMed2002

A trypanocidal phenazine derived from beta-lapachone.

An intensive effort has been directed toward finding alternative drugs for treatment of Chagas' disease, caused by Trypanosoma cruzi, and prophylaxis of blood in endemic areas. Our research comprises the synthesis and trypanocidal screening of derivatives from naphthoquinones. Herein a new phenazine, obtained from the reaction of beta-lapachone with aniline, has its structure established by physical data and X-ray analysis. It was 9 times more active against T. cruzi trypomastigotes than crystal violet.

Aniline Compounds↗

PubMedDate not supplied

A study on the antipicornavirus activity of flavonoid compounds (flavones) by using quantum chemical and chemometric methods.

The AM1 semiempirical method is employed to calculate a set of molecular properties (variables) of 45 flavone compounds with antipicornavirus activity, and 9 new flavone molecules are used for an activity prediction study. Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), Stepwise Discriminant Analysis (SDA), and K-Nearest Neighbor (KNN) are employed in order to reduce dimensionality and investigate which subset of variables should be more effective for classifying the flavone compounds according to their degree of antipicornavirus activity. The PCA, HCA, SDA, and KNN methods showed that the variables MR (molar refractivity), B(9) (bond order between C(9) and C(10) atoms), and B(25) (bond order between C(11) and R(7) atoms) are important properties for the separation between active and inactive flavone compounds, and this fact reveals that electronic and steric effects are relevant when one is trying to understand the interaction between flavone compounds with antipicornavirus activity and the biological receptor. In the activity prediction study, using the PCA, HCA, SDA, and KNN methodologies, three of the 9 new flavone compounds studied were classified as potentially active against picornaviruses.

Antiviral Agents↗