Antioxidant-Rich Polyfloral Bee Pollen Exerts Antimicrobial Activity and Anti-Inflammatory Effect in A549 Lung Epithelial Cells by Modulating the NF-κB Pathway

Bee pollen is produced by honeybees from the agglutination of pollen grains belonging to one or more plant species. Although it is intended to be a nutritional source for the hive, its remarkable concentration of nutrients and phytochemicals, combined with its pleasant organoleptic qualities, makes it appealing for human consumption. This study examined the phytochemical content and the antioxidant and antimicrobial activities of a polyfloral bee pollen collected in Tuscany (Italy). Additionally, its less studied anti-inflammatory potential towards tumor necrosis factor-alpha (TNF-α)-inflamed A549 cells was evaluated to assess its possible use in inflammatory respiratory diseases. Bee pollen extract (BPE) was chemically characterized in terms of total polyphenol (20.2 ± 1.5 mg gallic acid equivalents/g fw), flavonoid (9.22 ± 0.64 mg quercetin equivalents/g fw), and carotenoid (10.4 ± 1.4 µg carotenoids/g fw) contents. BPE exerted good antioxidant and antiradical activities in ferric reducing antioxidant power (38.6 ± 4.5 mg Fe2+/g fw), oxygen radical absorbance capacity (433.77 ± 18.95 μmol TE/g fw), and 2,2-diphenyl-1-picrylhydrazyl (EC50 = 613.8 ± 79.2 μg/mL) assays. Additionally, BPE inhibited the growth of Bacillus subtilis and Pseudomonas stutzeri (MIC = 10 mg/mL) in the microdilution assay. When TNF-α-inflamed A549 cells were pretreated with BPE (10 and 50 µg/mL), the upregulated interleukin-8 gene and cyclooxygenase-2 gene and protein expression were significantly attenuated. BPE modulated the nuclear factor-κB signaling pathway by decreasing its active phosphorylated form levels. These encouraging results confirm that honeybee pollen is a valuable health-promoting food that could alleviate the inflammatory component of various chronic pulmonary conditions.