Evaluación de la actividad antibacteriana sobre bacterias Gram negativas de extractos lipofílicos a partir del Desmodium molliculum

Natural products are in general, an important source for obtaining bioactive compounds to mitigate different health problems, such as bacterial resistance. In this work, the antibacterial activity of lipophilic extracts of Desmodium molliculum on bacterial strains of E. coli strain ATCC 25922 and S. Typhimurium strain ATCC 14028 was evaluated. The main method used to obtain these extracts was Supercritical Fluid Extraction (SFE). Two of the extractive conditions, such as pressure and amount of cosolvent (cosolvent 7%, 8.5% and 10%; pressure 50 bar, 100 bar, 150 bar), were modified in order to evaluate their influence in extract composition. The obtained extracts were evaluated against percolation, a classical method. The presence of metabolites (mono-sesquiterpenes and triterpenes, and phospholipids) that could be related to the antibacterial property of the different lipophilic extracts obtained by SFE was determined using a qualitative identification method as Thin Layer Chromatography (TLC). In spite of the fact, that different extractive variables and extraction conditions were analyzed, when antibacterial activity by the broth microdilution technique was evaluated, the extracts did not present the mentioned activity. Considering the biological activity reported to this genus, the active biomolecules of this plant present other activities and not necessarily the evaluated activity. When the extractive methods were compared, TLC plates showed higher intensity on the bands corresponding to SFE.