In vitro screening of herbal medicinal products for their supportive curing potential in the context of SARS-CoV-2

Abstract

Background Herbal medicinal products have a long-standing history of use in the therapy of common respiratory infections. In the COVID-19 pandemic, 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 (ACE2) receptor with the SARS-CoV-2 Spike S1 protein, ii) modulate the release of the human defensin HBD1 and cathelicidin LL-37 from human A549 lung cells upon Spike S1 protein stimulation and iii) modulate the release of IFN-γ 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 and the human ACE2 receptor was measured by ELISA. The effects on intracellular IFN-γ expression in stimulated human PBMCs were measured by flow cytometry. Regulation on HBD1 and LL-37 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 and the ACE2 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 IFNγ from stimulated PBMC. Co-treatment of A549 cells with IMU or BRO TP together with SARS-CoV-2 spike protein significantly upregulated mRNA expression (IMU) and release (IMU and BRO TP) of HBD1 and LL-37 (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 or supportive in recovery from SARS-CoV-2 infection needs deeper understanding of the observations.