Antioxidative Effect And First Evidence Of Synergistic Antimicrobial Effects Of Ficus Carica (L.) Leaf Essential Oil With Conventional Antibiotics

Ficus carica is one of the oldest and earliest cultivated fruits in the world. To our knowledge, little information is available on the antimicrobial and antioxidant activities of F. carica leaf essential oil (EO). Also, the potential synergistic interaction of this EO with standard antibiotics against multidrug resistant bacteria and clinically pathogenic yeasts has not been investigated. The characterization of the EO with GC/MS analyses led to identification of 35 components, representing 98.1 % of the total oil, with ficusin (32.8 %), caryophyllene oxide (9.0 %), bergapten (6.1 %) as major constituents. Regarding the antioxidant property, F. carica leaf EO showed moderate activity, as measured by DPPH free radical scavenging (1.45 +/- 0.05 mg/mL), beta-carotene/linoleic acid (1.56 +/- 0.09 mg/mL) and reducing power assays (1.92 +/- 0.13 mg/mL). The antimicrobial tests showed that EO presented higher activity against all tested microorganisms with MIC values ranging from 4.75 mg/mL to 38 mg/mL. The combination between conventional antibiotics and EO showed a high synergistic effect, especially against the Gram-positive bacteria, with FICI values ranged from 0.312 to 0.750. Interestingly, F. carica leaf oil has strongly reduced the known antibiotic MICs by 1 to 16-fold.