South African Propolis: Anti-Helicobacter pylori Activity, Chemistry, and Toxicity

Propolis, a resin-like substance produced by bees, has previously shown antimicrobial activity against the ulcer-causing gut pathogen Helicobacter pylori. South African propolis, however, was yet to be investigated. This study aimed to investigate a comprehensive range of South African propolis for its antimicrobial activity against H. pylori and to investigate toxicity. A total of 51 samples were collected from around South Africa and comparatively analysed with three Brazilian samples. The antimicrobial broth microdilution assay was used to determine the minimum inhibitory concentration (MIC) of ethanolic propolis extracts against three clinical H. pylori strains. A total of 27 South African propolis extracts presented antimicrobial activity better than that of the Brazilian samples (MIC ≤ 0.51 mg/mL). Samples with the best anti-H. pylori activity were selected for chemical analysis using ultra-performance liquid chromatography-mass spectrometry. The compounds pinocembrin, 3-O-acetylpinobanksin, and pinobanksin were found to be the most abundant. All propolis extracts investigated in this study were considered non-toxic (mortality < 50%) when investigated using the brine shrimp lethality assay. This study demonstrates the in vitro potential of utilizing propolis for treating H. pylori infections and highlights the possible compounds responsible for the activity observed.