Planta Med 2013; 79 - PG5
DOI: 10.1055/s-0033-1352075

Theoretical study of structural α-and β-cubebin isolated from Aristolochia esperanzae Kuntze

AG Pacheco 1, RT Nunes 1, AC Alcantara 2, D Pilo Veloso 2
  • 1Federal Institute for Education, Science and Technology in Southern Minas Gerais – Inconfidentes MG/Brazil.
  • 2Federal University of Minas Gerais, Belo Horizonte MG/Brazil

Rheumatoid arthritis (RA) causes severe physical disabilities. Ethnopharmacological studies indicate use of Aristolochia esperanzae Kuntze in treating RA. Phytochemical analysis of the stems of A. esperanzae provide a mixture of β-cubebin (1) and α-cubebin (2). This paper presents calculation results in different methods for structural analysis of these substances and of research of preferred positions of interaction between the molecule (2) and solvents. The calculations were performed using the software package of Gaussian 03W1.

Chemical shift calculations were performed using different methods and structures in gaseous state without intermolecular interactions. The data obtained with optimized geometries in different methods have been correlated with experimental 13C-NMR shift data that are in literature2. The best correlation coefficients (R2, Table 1) indicate most appropriate method to study of these substances.

Tab. 1: Correlation coefficients (R2) obtained for 1 and 2

Compound/Method

Level of calculation

HF

BLYP

B3LYP

PBE

1

0,98449

0,98676

0,99739

0,99119

2

0,98437

0,98521

0,99667

0,98665

The best level of calculation (B3LYP/6 – 31G*), indicated by better correlations, was used to determine the geometry of isolated phytochemicals – (8R,8'R,9S)-cubebin (1) and (8R,8'R,9R)-cubebin (2).

The effect of the solvent was investigated by the explicit addition of one molecule of solvent acetone, dimethylsulfoxide and pyridine in different positions of interaction with (2) at the B3LYP/6 – 31G* level. The systems of (2) with solvent showed high correlation coefficients. The configurations with the best correlations indicate the positions of preferential interaction between this molecule and solvent (Figure 1).

Fig. 1: Structure of (8R, 8′R, 9R)-cubebin (2) and preferred positions of interaction between (2) and solvents acetone (A), pyridine (B) and dimethylsulfoxide (C).

Acknowledgements:

CNPq, UFMG, and IFSULDEMINAS

References:

[1] Gaussian 03, Revision C.01.

[2] Pascoli, I. C.; Nascimento, I. R.; Lopes, L. M. X. Phytochemistry 2006, 67, 735. Christiansson, A.; Bertilsson, J.; Svensson, B.