Investigation of functional groups, phenolic and flavonoid compounds, antioxidant and antimicrobial activity of Lavandula stricta essential oil: An “in vitro” study

The aim of this study was to determine the functional groups and qualitative identification, the amount of phenolic and flavonoid compounds, antioxidant and antimicrobial activity of Lavandula stricta essential oil. Essential factor groups were determined by Fourier transform infrared (FTIR) spectroscopy in the wavelength range of 500–4000 cm-1. Total phenols and flavonoids were measured by Folin-Ciocalteu and aluminum trichloride colorimetry, respectively. Antioxidant activity was also determined by two methods of free radical scavenging DPPH and ABTS. The peaks observed in Lavandula stricta essential oil confirmed the presence of O-H, C-H, C=O, C=C, C-C and C-O functional groups of bioactive compounds. The amount of phenol and flavonoids in total essential oil was 68.60±0.68 mg GAE/g and 19.10±0.52 mg QE/g, respectively. Antioxidant activity was also obtained based on the percentage of free radical scavenging DPPH and ABTS equal to 59.50±0.63 and 67.68±0.53, respectively. The antimicrobial activity of essential oil was evaluated by four methods disk diffusion, agar well, minimum inhibitory concentration and minimum bactericidal concentration. The results of measuring the antimicrobial activity of essential oil by disk diffusion and agar well showed that Gram-positive bacterium Staphylococcus aureus is the most sensitive strain to Lavandula stricta essential oil. The minimum inhibitory concentration of essential oil for Salmonella typhi, Pseudomonas aeruginosa, Listeria innocua, Staphylococcus aureus and Escherichia coli was equal to 3.125 mg/ml and for Bacillus cereus it was equal to 6.25 mg/ml. The minimum bactericidal concentrations for Listeria innocua, Pseudomonas aeruginosa and Salmonella typhi was equal to 100, 200 and 400 mg/ml, respectively, and for other bacteria (Staphylococcus aureus, Bacillus cereus and Escherichia coli) it was more than 400 mg/ml.