Floral Origin Determines the In Vitro Antibacterial Activity of Bee Pollen Collected From Western Oromia, Ethiopia

Bee pollen has been used as a medicine and food supplement. The biological activity and nutrient composition of bee pollen depend on its floral origin. Therefore, it was aimed to determine the phenolic and flavonoid content and antibacterial activities of methanolic (99.9%) extract of bee pollens among flora. Floral origin was identified using melissopalynological analysis. In vitro antibacterial activity was evaluated using the agar well diffusion assay. The findings showed that the bee pollen from Eucalyptus plants had the highest phenol (62.4 ± 0.5 mg gallic acid equivalent/100 g) and flavonoid (49.6 ± 0.2 mg quercetin equivalent/100 g) contents. In comparison, bee pollen from Bidens had the lowest phenol (27.5 ± 0.8 mg gallic acid equivalent/100 g) and flavonoid (18.8 ± 0.7 mg quercetin equivalent/100 g) contents. The diameter of the inhibition zone ranged from 6.6 ± 0.6 mm against Escherichia coli ATCC 25922 and Acinetobacter baumannii ATCC 17978 (Bidens spp.) to 23.3 ± 0.6 mm against Staphylococcus aureus ATCC 25923 (Eucalyptus spp.). Besides, it was shown that phenolic and flavonoid content and antibacterial activity were positively correlated. The results showed that the bee pollen with more phenolic and flavonoid content strongly inhibited the growth of bacterial strain.