Identification of Bioactive Compounds and Heavy Metal Concentrations in Propolis Ethanolic Extract Produced by...

Propolis is high in bioactive compounds that can be utilised for its therapeutic properties. Yet, there are still limited research done, especially on the Malaysian stingless bee propolis. The present study highlights the analysis of bioactive compounds and the assessment of heavy metals in propolis extracts produced by Malaysian stingless bees. The propolis samples of three stingless bee species, namely Tetrigona apicalis, Tetrigona binghami, and Homotrigona fimbriata of the same environmental and ecological conditions, were collected in Selangor, Malaysia. The aim of this study was to evaluate the concentrations of various compounds (carbohydrates, lipids, vitamin C, phenols, flavonoids, amino acids, and terpenoids) and to identify individual bioactive components using gas chromatography-mass spectrometry (GC-MS). It was found that lipids had the highest average concentrations in all the extracts, and over 30 active compounds were identified in the ethanolic propolis extracts when analysed using GC-MS. Several significant chemical groups were present in the propolis extracts that were investigated, such as ketones, terpenoids, hydrocarbons, carboxylic acids, and alkaloids. Besides, a significantly (p < 0.05) higher concentration of lead was found in H. fimbriata (0.026 ± 0.01 mg/L) compared to other samples. Heavy metal analysis demonstrated that H. fimbriata contained significantly higher Pb (0.026 ± 0.01 mg/L) compared to T. apicalis (0.024 ± 0.00 mg/L) and T. binghami (0.016 ± 0.00 mg/L). T. binghami had a significantly higher As concentration (0.002 ± 0.00 mg/L) than H. fimbriata, while Cd, Zn, and Cr levels were not significantly different across samples. All heavy metal concentrations were within permissible limits set by FAO/WHO and Malaysian Food Regulations. The presented results indicate that Malaysian stingless bee propolis is rich in phenolics, flavonoids, and other active compounds that could potentially contribute to various potent biological activities commonly exhibited by propolis. Further studies on propolis need to be carried out in the future for a better understanding of propolis applications in various sectors.