Comparative study of different Malaysian stingless bee propolis: Physicochemical characterization, phytochemical contents and antibacterial activity

Stingless bee propolis is known to contain a variety of bioactive compounds, including phenolic and flavonoids, which have been linked to its antibacterial properties. Nevertheless, the phytochemical compositions of stingless bee propolis are significantly influenced by a complex interplay of multiple factors such as geographical origin, floral source, and bee species. This study aimed to assess the physicochemical properties, phytochemical contents, and antibacterial activity of propolis from different stingless bee species found in the same environment and ecological system. The propolis samples obtained from Heterotrigona itama, Geniotrigona thoracica and Tetrigona apicalis were subjected to physicochemical analysis to determine the pH, moisture, lipid, resin, and wax contents. The total phenolic content (TPC) and total flavonoid content (TFC) were measured by Folin-Ciocalteu colorimetric and aluminium chloride methods, respectively. The antibacterial activity was determined using the agar well diffusion method against four Gram-positive bacteria, including Bacillus cereus, Micrococcus luteus, Streptococcus mutans, and Staphylococcus aureus. The physicochemical analysis of the propolis samples yielded the following results: moisture (12.17-16.45%), lipid (2.95-9.48%), resin (39.00-51.00%), wax (26.50-37.00%), and pH (5.07-5.61). Results revealed that propolis produced by G. thoracica displayed significantly higher moisture (16.45±0.38%), and resin contents (51.00±1.41%), as well as significantly lower percentage of lipid (2.95±0.12%), and wax content (26.50±0.71%). Similarly, G. thoracica propolis extract exhibited significantly higher TPC (200.70±0.06mg/mL GAE) and TFC (141.60±3.63mg/mL QE) values compared to the other propolis samples. Additionally, G. thoracica propolis extract was significantly active against B. cereus and M. luteus with inhibition zones of 15.00 and 16.00, respectively, and minimum inhibition concentration (MIC) of 390.63μg/mL. A strong correlation was found between resin content, TPC and antibacterial activity of propolis. This study indicated that the presence of high resin content in propolis resulted in a high concentration of phenolic compounds, which contributed significantly to its antibacterial activities. Furthermore, the research highlighted the species-dependent effect of propolis on its physicochemical characteristics, phytochemical composition, and antibacterial properties. The observed antibacterial efficacy of G. thoracica propolis suggested that the propolis extract held promise as an alternative treatment option against bacterial infections. Further research is warranted to fully elucidate the specific phenolic compounds that could contribute to its antibacterial properties.