ANTISTAPHYLOCOCCAL ACTIVITY OF DIFFERENT EXTRACTS FROM Cuspidaria convoluta LEAVES

TORRES, CAROLA ANALÍA; STURLA, MARIO ANÍBAL; ROMERO, ANA MARÍA; JUDIS, MARÍA ALICIA

Rosario

Encuentro; 4ª Reunión Internacional de Ciencias Farmacéuticas; 2016

Staphylococcus aureus is an opportunistic pathogen that causes several diseases in humans. This study was designed to evaluate the antistaphylococcal activity of different extracts [petroleum ether (PEE), ethyl acetate (EAE) and ethanol (EE)] obtained from Cuspidaria convoluta (Vell.) A. H. Gentry leaves. The antibacterial activity was determined by bioautography and micro-dilution method. Ten clinical isolates of Staphylococcus aureus, two methicillin-resistants (MRSA) and eight methicillin sensitives (MSSA), obtained from hospital patients of the Presidencia Roque Sáenz Peña city, were evaluated. The minimal inhibitory concentration (MIC) was determined using sterile 96-well microplates with inocula in Mueller Hinton broth, microplates were incubated at 37 °C for 16-20 h. The concentrations of extracts used were from 31.25 to 1000 μg/mL and bacterial growth was evaluated by turbidity and/or a pellet on the well bottom. The main antibacterial compounds were investigated by means of chromatographic and spectrophotometric techniques; they were identified by comparison with standards. Different mobile phases (chloroform:methanol 9:1, toluene: acetic acid: ethyl acetate 36:5:12 and ethyl acetate:formic acid:acetic acid:water 100:11:11:26) were used for thin layer chromatography (TLC). Reversed-phase HPLC with diode array detection using methanol and water/formic acid (0.1%, v/v) as mobile phase with a gradient program, and UV?VIS spectroscopy (200 to 400 nm) were carried out. The MIC values ranged between 125 μg/mL and 1000 μg/mL for EE and EAE. EAE was the most effective inhibiting even MRSA (MIC=250 µg/mL). Luteolin and chrysin were identified in EE, whereas apigenin and chrysin were identified in EAE. Also, one compound with the same retention time was found in both extracts, which presented characteristic UV absorption spectra similar to a phenolic acid. Subsequent studies in mass spectrometry to the compounds confirmation will be made. These substances could be responsible of the antibacterial activity of these extracts, which represents an important step in the search of a new antistaphylococcal agent.