Chemical Composition, Antibacterial and Antibiotic Potentiating Activity of the Essential Oil of Allium sativum L. Bulbils and Allicin

The present study aims to analyze the chemical profile, antibacterial activity, and modifying effect of the essential oil from the bulbils of Allium sativum L. in comparison with allicin. To this end, the plant was collected near the city of Caririaçu - CE and taken to the municipality of Juazeiro do Norte - CE for the experiments. Allicin was obtained from Sigma-Aldrich®. The bulbils were crushed and subjected to hydrodistillation using a modified Clevenger-type apparatus to obtain the essential oil. The antibacterial activity of the oil and the isolated compound was evaluated using the microdilution method against Gram-positive and Gram-negative bacteria. Finally, the modifying activity was determined in association with aminoglycoside and beta-lactam antibiotics. Regarding beta-lactams, results showed that the MIC of benzylpenicillin against Staphylococcus aureus was reduced from >1024 μg/mL to <1024 μg/mL. However, no activity was observed in several combinations, such as cefalotin and benzylpenicillin against Escherichia coli. For Pseudomonas aeruginosa, activity was observed in several combinations, including amikacin, with MIC reduction from 512 μg/mL to 256 μg/mL, and gentamicin, from 1024 μg/mL to 64 μg/mL. The combination of essential oil with antibiotics such as benzylpenicillin and amikacin can enhance antibacterial efficacy by altering bacterial membrane permeability. Allicin exhibited significant synergistic mechanisms when combined with aminoglycosides. Thus, further experiments with different bacterial strains are essential for the development of new therapies using garlic.