Abstract
In this study, we investigated the chemical composition, and antioxidant and antibacterial properties of ethanolic extracts of propolis (EEP) from Melipona quadrifasciata quadrifasciata and Tetragonisca angustula. Chemical composition of EEP was determined by colorimetry and chromatographic (HPLC-DAD and UPLC-Q/TOF-MS/MS) analysis. Antimicrobial activity of EEP was evaluated against gram-positive (S. aureus, methicillin-resistant S. aureus, E. faecalis) and gram-negative (E. coli and K. pneumoniae) bacteria by the minimal inhibitory concentration (MIC) test using the microdilution method. Furthermore, the growth curve and integrity of cell membrane of S. aureus and E. coli were investigated using standard microbiological methods. HPLC-DAD analysis showed that the EEP of M. quadrifasciata quadrifasciata has a more complex chemical composition than the EEP of T. angustula. Moreover, UPLC-MS analyses of M. quadrifasciata quadrifascita indicated flavonoids and terpenes as major constituents. The bactericidal activity of both EEPs was higher against gram-positive bacteria than for gram-negative bacteria. The EEP from M. quadrifasciata quadrifasciata presented MIC values lower than the EEP from T. angustula for all tested bacteria. The EEP from M. quadrifasciata quadrifasciata caused lysis of the bacterial wall and release of intracellular components from both E. coli and S. aureus. Our findings indicate that the chemical composition of propolis from stingless bees is complex and depends on the species. The extract from M. quadrifasciata quadrifascita was more effective against gram-positive than gram-negative strains, especially against S. aureus and methicillin-resistant S. aureus compared to T. angustula extract, by a mechanism that involves disturbance of the bacterial cell membrane integrity.
Highlights
Propolis is a complex mixture of pollen and resinous and balsamic substances collected by bees from buds, flowers, and plant exudates, and bee salivary secretions [1]
The current study revealed that ethanolic extracts of propolis (EEP) from M. quadrifasciata quadrifasciata and T. angustula had antimicrobial activity against gram-positive and gram-negative bacteria and antioxidant activity
The chemical analysis of the EEPs revealed the presence of terpenoids, flavonoids, and polyphenols, which were more abundant in the EEP from M. quadrifasciata quadrifasciata (Figure 1)
Summary
Propolis is a complex mixture of pollen and resinous and balsamic substances collected by bees from buds, flowers, and plant exudates, and bee salivary secretions [1]. Different biological and therapeutic properties have been reported for propolis, including antioxidant [3,5], antiinflammatory [5,6], immunomodulatory [7,8], antitumoral [8,9], and antimicrobial activities [2,7,10,11] among others. A synergistic inhibitory effect of propolis and antibiotics on the growth of S. aureus has been reported [11]. Such an antimicrobial activity of propolis is relevant if one considers the increasing emergence
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