# Chemical Characterization and Antibiotic-Enhancing Activity of the Essential Oils of Propolis of Melipona quadrifasciata quadrifasciata

## TL;DR

This study found that essential oils from a type of propolis can enhance antibiotics against bacteria, even though the oils alone aren't effective.

## Contribution

The study reveals that MQP essential oils enhance antibiotic efficacy, despite lacking direct antibacterial activity.

## Key findings

- MQP essential oils showed no antibacterial activity when used alone (MIC ≥ 1024 μg/mL).
- MQP oils enhanced the effectiveness of norfloxacin, gentamicin, and ampicillin, especially against Staphylococcus aureus.
- β-bisabolene and β-caryophyllene were the main compounds identified in the oils.

## Abstract

This study investigated the chemical composition and potential antibacterial activity of the essential oils from the propolis of Melipona quadrifasciata quadrifasciata (MQP) in samples collected from the cities of Paranaguá and Guaratuba, Paraná, Brazil, during summer and winter. The chemical composition of the oils was analyzed by GC-MS, and their minimum inhibitory concentration (MIC) was determined against standard ATCC strains and some clinical isolates (Escherichia coli 06 and Staphylococcus aureus 10). The essential oils’ MICs were determined using microdilution in 96-well plates and showed no significant antibacterial activity (MIC ≥ 1024 μg/mL) when used alone. However, the essential oils enhanced the action of norfloxacin, gentamicin, and ampicillin, especially against S. aureus 10. The chemical analysis identified 68 compounds, with β-bisabolene and β-caryophyllene as the predominant constituents. Subsequently, the antibiotic-enhancing activity against the clinical isolates was evaluated. The composition of the MQP oils varied according to seasonality and location, influenced by the microclimates of the cities. The results highlight the importance of MQP oils in enhancing antibiotic activity, particularly against Gram-positive bacteria, despite the lack of significant standalone antibacterial activity.