Chemical analysis, antibacterial, and antioxidant activities of flavonoid-rich extracts from four Moroccan propolis

Propolis, a resinous substance collected by honeybees from plants, is well-known worldwide for its diversified biological activities. This study was aimed to determine the chemical composition of four ethanol extracts of propolis collected from Morocco and to investigate their antibacterial and antioxidant activities. The chemical composition was determined by Ultra-High Performance Liquid Chromatography-tandem mass spectrometry. The antibacterial activity was evaluated using the well diffusion and microdilution methods. The antioxidant activity was investigated in vitro using three complementary techniques, namely reduction power, beta-carotene bleaching, and DPPH scavenging assays. The identified molecules belong mainly to the flavonoid family, and interestingly, several of them were flavonoid glycosides. The four extracts showed strong antibacterial activity. The inhibitory zones varied from 10.00 +/- 00 to 22.5 +/- 2.12 mm, and minimal inhibitory concentration values ranged from 0.15 to >5 mg/ml, while minimal bactericidal concentration values ranged from 1.25 to >5 mg/ml. The antioxidant activity was relatively strong compared to positive controls, with IC50 varied from 67.61 to 140.04 mu g/ml against DPPH free radical, and a relative antioxidant activity varied from 68.40 +/- 3.90 to 100.92 +/- 4.24, determined by beta-carotene bleaching test. The antioxidant property was related to the chemical constituents. These results indicate that Moroccan propolis can be a valuable source of bioactive compounds for further drug discovery. Novelty impact statement More than 100 compounds have been identified in Moroccan propolis extracts. Trigonelline (an alkaloid) was identified for the first time in propolis. Propolis extracts exhibited strong antibacterial and antioxidant activity.