Background: Herbal medicinal products have a long-standing history of use in the therapy of common
respiratory infections MESHD. In the
COVID-19 pandemic MESHD, they may have the potential for symptom relief in non-severe or moderate disease cases. Here we describe the results derived by in vitro screening of five herbal medicinal products with regard to their potential to i) interfere with the binding of the human
Angiotensin-converting enzyme 2 HGNC (
ACE2 HGNC) receptor with the
SARS-CoV-2 Spike MESHD SARS-CoV-2 Spike PROTEIN S1 protein PROTEIN, ii) modulate the release of the human defensin HBD1 and cathelicidin
LL-37 HGNC from human A549 lung cells upon
Spike S1 protein PROTEIN stimulation and iii) modulate the release of
IFN-{gamma HGNC} from activated human peripheral blood mononuclear cells (PBMC). The investigated extracts were: Sinupret extract (SINx), Bronchipret thyme-ivy (BRO TE), Bronchipret thyme-primrose (BRO TP), Imupret (IMU), and Tonsipret (TOP). Methods: The inhibitory effect of the herbal medicinal products on the binding interaction of
Spike S1 protein PROTEIN and the human ACE2 receptor was measured by ELISA. The effects on intracellular
IFN-{gamma HGNC} expression in stimulated human PBMCs were measured by flow cytometry. Regulation on
HBD1 HGNC and
LL-37 HGNC expression and secretion was assessed in 25d long-term cultured human lung A549 epithelial cells by RT-PCR and ELISA. Results: IMU and BRO TE concentration-dependently inhibited the interaction between
spike protein PROTEIN and the
ACE2 HGNC Receptor. However, this effect was only observed in the cell-free assay at a concentration range which was later on determined as cytotoxic to human PBMC. SINx, TOP and BRO TP significantly upregulated the intracellular expression of antiviral
IFN{gamma HGNC} from stimulated PBMC. Co-treatment of A549 cells with IMU or BRO TP together with
SARS-CoV-2 spike MESHD SARS-CoV-2 spike PROTEIN protein significantly upregulated mRNA expression (IMU) and release (IMU and BRO TP) of
HBD1 HGNC and
LL-37 HGNC (BRO TP). Conclusions: The in vitro screening results provide first evidence for an immune activating potential of some of the tested herbal medicinal extracts in the context of SARS-CoV-2. Whether these could be helpful in prevention of
SARS-CoV-2 invasion MESHD or supportive in recovery from
SARS-CoV-2 infection MESHD needs deeper understanding of the observations.