Evaluation of Antimicrobial and Antioxidant Potential of Essential Oil from Croton piauhiensis Müll. Arg.

A large number of infections are caused by Gram-positive and Gram-negative multi-resistant bacteria worldwide, adding up to a figure of around 700,000 deaths per year. The indiscriminate uses of antibiotics, as well as their misuse, resulted in the selection of bacteria resistant to known antibiotics, for which it has little or no treatment. In this way, the strategies to combat the resistance of microorganisms are extremely important and, essential oils of Croton species have been extensively studied for this purpose. The aim of this study was to carry the evaluation of antibacterial, antibiofilm, antioxidant activities, and spectroscopic investigation of essential oil from Croton piauhiensis (EOCp). The EOCp exhibited antimicrobial activity against Gram-positive and Gram-negative bacteria with required MICs ranging from 0.15 to 5% (v/v). In addition, the MBC of the EOCp for Staphylococcus aureus ATCC 25923 and ATCC 700698, were 0.15 and 1.25%, respectively. Moreover, the EOCp significantly reduced significantly the biofilm production and the number of viable cells from the biofilm of all bacterial strains tested. The antioxidant potential of the EOCp showed EC50 values ranging from 171.21 to 4623.83 µg/mL. The EOCp caused hemolysis (>45%) at the higher concentrations tested (1.25 to 5%), and minor hemolysis (17.6%) at a concentration of 0.07%. In addition, docking studies indicated D-limonene as a phytochemical with potential for antimicrobial activity. This study indicated that the EOCp may be a potential agent against infections caused by bacterial biofilms, and act as a protective agent against ROS and oxidative stress.

Antibiofilm activity of the essential oil of citronella (Cymbopogon nardus) and its major component, geraniol, on the bacterial biofilms of Staphylococcus aureus.

Medicinal plants with antimicrobial action have been investigated for uses against biofilms, among which, Cymbopogon nardus, citronella, stands out as a promising species. The present study aims to evaluate the antimicrobial and antibiofilm action of the essential oil of C. nardus (EOCN) and geraniol on Gram-negative and positive bacteria from the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration and inhibition of biofilms. In the results, the EOCN produced a 41 mm halo on S. aureus, which was susceptible with MIC values of 0.5 and 0.25 mg/mL for the EOCN and geraniol respectively, both with bactericidal effect. The antibiofilm action was confirmed, the EOCN and geraniol reduced the biofilm biomass of S. aureus up to 100% between 0.5 and 4 mg/mL concentrations. The reduction of cell viability was 0.25 and 1 mg/mL, of EOCN and geraniol, respectively. EOCN and geraniol were shown to be promising antibiotic against S. aureus.