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

• Published in: Planta Medica
• Main Authors: Pacheco, AG, Nunes, RT, Alcantara, AC, Pilo Veloso, D
• Format: Conference Proceeding
• Language: English
• Published: 21.08.2013
• ISSN: 0032-0943; 1439-0221
• DOI: 10.1055/s-0033-1352075

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 03W 1 . 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 literature 2 . The best correlation coefficients (R 2 , Table 1) indicate most appropriate method to study of these substances. 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 – (8 R ,8' R ,9 S )-cubebin ( 1 ) and (8 R ,8' R ,9 R )-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 (8 R , 8′ R , 9 R )-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.