Antimicrobial Activity and Nutraceutical Potential of Tuscan Bee-Pollens on Oxidative and Endoplasmic Reticulum Stress in Different Cell-Based Models
Bee-pollen is an apiary product of great interest owing to its high nutritional and therapeutic properties. This study aimed to assess the cellular antioxidant activity and the antihemolytic effects of Castanea, Rubus, and Cistus bee-pollens on oxidized human erythrocytes. In addition, the antimicrobial potential of each sample was tested on three Gram-negative and two Gram-positive bacteria. Finally, the effect of Castanea bee-pollen, showing better phytochemical content, was analyzed on human microvascular endothelial cells (HMEC-1) exposed to thapsigargin, used to induce endoplasmic reticulum stress (ER-stress). Our results showed good biological activities of all bee-pollen samples, which, under oxidative conditions, significantly improved the erythrocytes’ antioxidant activity and limited cell lyses. Moreover, all samples exerted antimicrobial activity with different selectivity among the tested microorganisms, with minimal inhibitory concentration values ranging from 5 to 10 mg/mL. Finally, thapsigargin treatment increased intracellular ROS (reactive oxygen species) production and up-regulated the expression of factors involved in the ER-stress and inflammatory pathways. Conversely, Castanea bee-pollen was effective in reducing gene overexpression, as well as the oxidation process arising from thapsigargin treatment, with a maximum protective effect at 10 µg/mL. In conclusion, bee-pollens, mainly Castanea species, represent good natural antibacterial and potential nutraceutical products useful in the prevention of free radical and ER-stress associated diseases.