In vitro anti-inflammatory and anti-microbial activity of cowslip flowers (Primula veris L.)
Flowers of Primula veris L. are part of the medicinal product Sinupret®, an herbal remedy to treat acute and chronic inflammations of the paranasal sinuses.
In this study, a Primulae flos dry extract (PFE) was tested in vitro for inhibition of prostaglandin biosynthesis by cyclooxygenases (COX-1 and -2) and for inhibition of leukotriene biosynthesis in human polymorphonuclear leukocytes. Furthermore, the T-cell mediated release of the pro-inflammatory cytokines IFN-γ and GM-CSF from human peripheral blood mononuclear cells was studied after incubation with PFE. In addition, in vitro anti-microbial activity of PFE was studied in virus plaque-reduction assays [human rhinovirus (HRV), respiratory syncytial virus (RSV)] and in microdilution assays for determination of minimum bactericidal concentration (MBC; targets: Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae).
PFE efficiently inhibited viral replication (EC50,HRV=58µg/mL and EC50, RSV=62µg/mL) and displayed anti-bacterial activity with MBC of 200µg/mL. The targeted viruses and bacteria are involved in respiratory tract infection thus pointing to the therapeutic potential of PFE in this field. PFE significantly reduced IFN-γ and GM-CSF secretion in a dose-dependent manner and inhibited prostaglandin synthesis as well as leukotriene formation, thus showing a broad anti-inflammatory impact. Taken together, for the treatment of respiratory infections, PFE might act via a direct anti-microbial effect and also by inhibiting the inflammatory sequelae.