Antibacterial and Antioxidant Activities of Ethanolic and Water Extracts of Stingless Bees Tetrigona binghami, Heterotrigona itama, and Geniotrigona thoracica Propolis Found in Brunei

Abstract

In the present study, the antibacterial activities of ethanolic and water extracts of propolis produced by stingless bees Tetrigona binghami, Heterotrigona itama, and Geniotrigona thoracica found in Brunei against four different bacterial strains were quantified. Additionally, spectroscopic and colorimetric methods, including Fourier transform infrared, absorption, fluorescence, aluminum chloride, and Folin-Ciocalteu analyses were used to characterize the propolis extracts. Flavonoid, phenolic, and aromatic acid compounds in the propolis extracts were also quantified, as these compounds are responsible for their antioxidant capacity. The antibacterial activity was determined based on bacterial growth inhibition zones using the disc diffusion, and it was further confirmed by the minimum inhibitory and bactericidal concentrations, which were evaluated using the broth macrodilution method. The propolis extracts exhibited antibacterial activities but were lower compared to streptomycin, which was used as a standard antibiotic. The MIC values of the water extracts were 2500 μg/mL, and those of the ethanolic extracts were in the range of 2500‒10000 μg/mL, much higher than other reported propolis from different countries. Their MBC test further suggested that the propolis extracts were bacteriostatic. The overall findings evidenced the quantities of the antibacterial and antioxidant properties of the propolis extracts, although the results suggested low antibacterial activities of the propolis extracts from Brunei stingless bees.