Antibacterial activity of natural anthraquinones

COMINI, L.R.; NÚÑEZ MONTOYA, S.C.; PÁEZ P.L.; ÁLBESA, I.; CABRERA, J.L.

Córdoba, Argentina

Simposio; X SIMPOSIO ARGENTINO y XIII LATINOAMERICANO DE FARMACOBOTANICA; 2010

Facultad de Ciencias Químicas-UNC

The photodynamic antimicrobial chemotherapy involves photosensitizers (PS) and visible or ultraviolet light and has been proposed in the treatment of locally occurring infections (caries, periodontal diseases, oral candidiosis) and infected wounds. Some PS produces bacterial photoinactivation through a photodynamic photosensitization acting mainly through the generation of reactive oxygen species (ROS), particularly singlet molecular oxygen (1O2)1. Heterophyllaea pustulata Hook. f. (Rubiaceae) is a phototoxic vegetal species popularly known as “cegadera”. From leaves and stems nine anthraquinones (AQs): soranjidiol, soranjidiol-1-methyl ether, rubiadin, rubiadin-1-methyl ether, damnacanthal, damnacanthol, heterophylline, pustuline and 5,5´-bisoranjidiol were isolated and identified2,3. In complementary studies we have demonstrated that these AQs exhibit photosensitizing properties by generation of superoxide anion (O2•_) and/or 1O24,5. Our aim was to determine whether the isolated AQs from H. pustulata have antibacterial effect on Staphylococcus aureus ATCC 29213 and whether this effect is due solely to a photodynamic process or to a concurrent combination between both driven processes: under irradiation and darkness. Bactericide activity was determined by counting the colony-forming units per milliliter (cfu/mL) in plate. The O2•_ production was determined by means of an indirect photobiological assay (Nitroblue Tetrazolium test), and the production of 1O2 was followed using an indirect method in a stationary state, with methionine as the 1O2 chemical quencher. All experiments were carried out in darkness and under irradiation. Four AQs out of nine: soranjidiol, rubiadin, damnacanthal and 5,5´-bisoranjidiol, showed antibacterial activity (bacteriostatic/bactericide) on S. aureus. Our results proved that upon AQs addition to bacteria there is usually an increase in the level of O2•_ and/or 1O2 which is further augmented by light. Moreover, our results suggest that, among the different species that comprise ROS, 1O2 is the one mainly involved in the bactericidal effect as has been already reported by Becerra et al.6 using S. aureus too. Referencias 1) Pellieux, C., A. Dewilde, Ch. Pierlot & J-M. Aubry. 2000. Methods Enzymol. 319: 197-207. 2) Núñez Montoya, S., A. Agnese, C. Pérez, I. Tiraboschi & J. Cabrera. 2003. Phytomedicine 10: 569-574. 3) Núñez Montoya, S., A. Agnese & J. Cabrera. 2006. J. Nat. Prod. 69: 801-803. 4) Núñez Montoya, S., L. Comini, M. Sarmiento, M. Becerra, I. Albesa, G. Argüello & J. Cabrera. 2005. J. Photochem. Photobiol. B: Biol. 78: 77-83. 5) Comini, L., S. Núñez Montoya, M. Sarmiento, J. Cabrera & G. Argüello. 2007.  J. Photochem. Photobiol. A: Chem. 188: 185-191. 6) Becerra, M., M. Sarmiento, P. Páez, G. Argüello & I. Albesa. 2004. J. Photochem. Photobiol. B: Biol. 76: 13-18.