Establishing indicators of propolis content collected by honey and stingless bees in Thailand

Various bee products, including propolis, are regularly consumed by humans as medical treatments. Yet it remains a challenge to predict the efficacy of the active ingredients of these natural bee products because the contents can vary based on environmental conditions and bee species. Therefore, this study aims to characterize and directly compare the content of propolis produced by Apis mellifera and Tetragonula pagdeni located in agricultural and non-agricultural areas throughout Thailand during the dry and wet seasons. Cadmium (Cd) and lead (Pb) were analyzed using a flame atomic absorption spectrophotometer. Total phenolic content (TPC) and total flavonoid content (TFC) were evaluated. Antioxidant activity was assessed using the DPPH radical-scavenging assay and expressed as EC50. HPLC was also used to obtain chromatographic profiles of the propolis samples. Our findings showed that Cd and Pb were not detected in any sample, whereas TPC, TFC, and EC50 varied from 18.33 ± 1.36 to 116.56 ± 5.83 mg GAE/g, 4.68 ± 0.10 to 113.63 ± 5.86 mg QE/g, and 1.01 ± 0.11 to 30.61 ± 0.43 mg/mL, respectively. Propolis from T. pagdeni showed higher content and stronger DPPH radical-scavenging activity than that from A. mellifera. Samples collected from non-agricultural areas and in the dry season also tended to exhibit higher bioactivity. HPLC analysis further revealed variation in the chromatographic profiles among samples. These findings help predict when and where to collect propolis to maximize its effectiveness as a functional natural product, as well as providing new knowledge about its ecological sensitivity.