Antibacterial activity of aerial parts of Aspidosperma quebracho-blanco

Abstract

Aspidosperma (Apocynaceae) comprises 24 species distributed from México to Argentina. Several species of Aspidosperma showed antimicrobial activity. The antibacterial activity of A. quebracho-blanco was not yet characterized. In this work, the effect of aerial parts of A. quebracho-blanco was evaluated on several phytopathogenic bacteria. Leaves and stems of A. quebracho-blanco were separated and ground. These materials were sequentially extracted with dichloromethane, ethyl acetate and metanol. The organic extracts were evaporated to dryness and known amounts of the dry residues were dissolved in etanol, obtaining fractions fCH2Cl2, fAcet y fMeOH, respectively. The last ones were assayed by the microdilution method with Mueller-Hinton semiliquid medium. (4000-2,9 ppm) on strains of CECT 225 (Erwinia carotovora var carotovora), CECT 124 (Pseudomonas corrugata), CECT 126 (Pseudomonas syringae pv tomato) and Agrobacterium tumefaciens using suspensions of 107 UFC/mL. The IC50 was calculated by probit analysis. Ciprofloxacin was used as positive control (250-62 ppm).The CI50s of fCH2Cl2, fAcet and fMeOH from stem, and fCH2Cl2 and fAcet from leaves were higher than 4000 ppm for Agrobacterium tumefaciens, Erwinia carotovora and Pseudomonas syringae. The fMeOH fromleaves showed IC50 of 3261 ppm on Pseudomonas syringae. In the case of Pseudomonas corrugata, the IC50 of fCH2Cl2 from stems and leaves, and fAcet and fMeOH from leaves were 2460, 3138, 2728 and 3258 ppm, respectively. The isolation and identification of the bioactive molecules is in progress.