SARS-CoV-2 inhibitory, anti-inflammatory, antibacterial activity of black chokeberry (Aronia melanocarpa (Michx.) Elliott) branches’ extracts and proanthocyanidins, and their synergistic interaction with antibiotics

Bacteria and viruses' potential collaboration has been reported to result in enhanced infection pathogenesis. New antimicrobial agents are necessary, but stronger synthetic antibiotics cause more severe side effects. The relevance of natural agents has increased in the post-COVID-19 period also due to COVID-induced cytokine storm, causing severe complications. This study aimed to evaluate Aronia melanocarpa branches for producing anti-SARS-CoV-2, anti-inflammatory, and antimicrobial preparations, and their synergistic activity with antibiotics. Biomass water and water-ethanol extracts were analyzed for total polyphenols, tannins, individual compounds (UHPLC-MS/MS), content of functional OH groups. Anti-SARS-CoV-2 activity was tested using SARS-CoV-2 (2019-nCoV) Inhibitor Screening ELISA Kit, anti-inflammatory activity - in peripheral blood mononuclear cells (PBMNC) under normal and inflammatory conditions; antimicrobial and synergistic efficacy with antibiotics were tested against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA). Oligomeric proanthocyanidins were dominant compounds in the extracts, with the highest concentration in autumn samples (35% per dry extract). The extracts and oligomeric proanthocyanidins were effective in inhibiting the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein and regulating inflammatory processes caused by viral and bacterial infections, including the reduction of IL-6 and regulation of IL-10 secretion. Proanthocyanidins and extracts exhibited significant anti-biofilm activities and showed synergistic activity with antibiotics.