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.