Composition, Antibiofilm, and Antibacterial Potential of Volatile Oils from Geopropolis of Different Stingless Bees' Species.

We aimed to characterize and investigate the antibacterial potential of the native stingless bees geopropolis volatile oils (VO) for the search of potentially new bioactive compounds. Geopropolis samples from Melipona bicolor schencki, M. compressipes manaosensis, M. fasciculata, M. quadrifasciata, M. marginata and M. seminigra merrillae were collected from hives in South Brazil. VO were obtained by hydrodistillation and characterised by gas chromatography coupled to mass spectrometry (GC/MS). Antimicrobial activity was assessed by microplate dilution method. The lowest MIC against cell walled bacteria was 219±0 µg mL-1 from M. quadrifasciata geopropolis VO with Staphylococcus aureus. The M. b. schencki geopropolis VO minimal inhibition concentration (MIC) was 424±0 µg mL-1 against all the mycoplasma strains evaluated. Fractionation resulted in the reduction of 50 % of the MIC value from the original oil. However, its compounds' synergism seems to be essential to this activity. Antibiofilm assays demonstrated 15.25 % eradication activity and 13.20 % inhibition of biofilm formation after 24 h for one subfraction at 2× its MIC as the best results found. This may be one of the essential mechanisms by which geopropolis VOs perform their antimicrobial activity.

Antimicrobial Activity of Volatile Oils from Brazilian Stingless Bees Melipona quadrifasciata quadrifasciata and Tetragonisca angustula Propolis.

Few studies were performed on the volatile components' properties of propolis from native Brazilian stingless bees. This work sought to extract, chemically characterize, and evaluate of the antimicrobial properties of volatile oils from propolis of the stingless bees Melipona quadrifasciata quadrifasciata (MQ) and Tetragonisca angustula (TA). The volatile oils from the pulverized propolis samples were obtained in a Clevenger apparatus and characterized by gas chromatography coupled to mass spectrometry (GC/MS) and to flame ionization detector (GC-FID). All samples showed promising activity against Mycoplasma pneumoniae, with MICs from 103 to 224 µg mL-1 , nonetheless, they were less active against cell walled bacteria. Activity against Candida species was moderate, but one MQ sample showed a MIC value of 103 µg mL-1 against C. tropicallis. Oils' fractionation showed no improvement in antibacterial activity. The promising antibacterial effect against this microorganism is likely related to the synergism between the components of the volatile oils.