Extract of Pelargonium sidoides (EPs® 7630) improves phagocytosis, oxidative burst, and intracellular killing of human peripheral blood phagocytes in vitro

Clinical data show that EPs® 7630, an aqueous ethanolic extract from the roots of Pelargonium sidoides, can be used for the treatment of upper respiratory tract infections (URTI). The biological effects of the preparation have not been fully investigated. The objective of this study was to examine the impact of EPs® 7630 on the activity of human peripheral blood phagocytes (PBP).A whole blood-based, flow cytometric assay was used to simultaneously assess phagocytosis and oxidative burst. Calcein-AM stained Candida albicans (DSM 1386) were used as target organisms. Oxidative burst was measured by addition of dihydroethidium (DHE). Target organisms and whole blood were co-incubated and analyzed after 0, 2, 4, 6, 10, and 30 min. Intracellular killing of the target organisms was evaluated by determining the number of surviving yeast cells after co-incubation of C. albicans and human whole blood. EPs® 7630 was applied in therapeutically relevant concentrations between 0 and 30 μg/ml.Compared with controls EPs® 7630 increased the number of phagocytosing PBP during the observed time points between 2 and 10 min in a concentration-dependent manner, with a maximum enhancement of 56% at 2 min (p=0.002p=0.002). The application of EPs® 7630 also led to a significant increase in the number of burst-active PBP for all time points observed beyond 2 min (p<0.001p<0.001). The maximum augmentation was 120% after application of 30 μg/ml EPs® 7630 at 4 min. Using a microbiological assay, intracellular killing was also enhanced by EPs® 7630. This was expressed by a significant reduction in the number of surviving target organisms (p<0.001p<0.001). The maximum reduction in viable yeast cells (−31%) was observed after co-incubation for 120 min with the highest concentration of EPs® 7630 (30 μg/ml).In conclusion, the positive effects of EPs® 7630 on phagocytosis, oxidative burst, and intracellular killing of yeast cells as test organisms are important components of the compound's biological activity. Our findings constitute a valuable contribution to understanding the clinical effects of EPs® 7630.