Cinnamon and Hop Extracts as Potential Immunomodulators for Severe COVID-19 Cases
Kurt Lucas, Janine Fröhlich‐Nowoisky, Nicole Oppitz, Maximilian Ackermann
Abstract
Despite intense focus, so far no effective treatment has been developed for severe cases of COVID-19. SARS-CoV-2 infection results in a multisystem hyperinflammatory syndrome with acute respiratory distress syndrome (ARDS), acute kidney failure, and cardiovascular and neurological complications (Wang et al., 2020). Severe cases of this condition are characterized by a “cytokine storm” and rampant inflammation (Renu et al., 2020; Ye et al., 2020). The hyperinflammation is associated with the generation and release of reactive oxygen and nitrogen species (ROS/RNS), which can further amplify inflammation (Lucas and Maes, 2013). Histopathological observation of COVID-19 has revealed diffuse alveolar damage with vascular endothelialitis, thrombosis, and intussusceptive angiogenesis (Ackermann et al., 2020). The angiocentric inflammation is not limited to the COVID-19-induced lung injury but also involves prolonged inflammation in other organs, such as the liver, brain, heart, or the gut (Ackermann et al., 2020; Wang et al., 2020). Any treatment that could limit the “cytokine storm,” reduce ROS/RNS production, and counteract the formation of thrombosis would be highly attractive, and, in the best-case scenario, such a treatment would additionally interfere with viral replication. Recently, a preliminary study reported that the administration of dexamethasone, a corticosteroid with anti-inflammatory effects, could elicit a 30% reduction in mortality for patients receiving invasive mechanical ventilation (Horby et al., 2020). In a previous study, we screened a panel of 99 ethanolic herbal extracts for their anti-inflammatory properties. Hop (Humulus lupulus, cones) and Ceylon cinnamon (Cinnamomum verum alias C. zeylanicum, bark) extracts were found to elicit particularly drastic reductions in activation of the transcription factor NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), a key regulator of pro-inflammatory cytokines (Schink et al., 2018b). The literature search was mainly performed in MedLine. In a first round, we looked for studies describing anti-inflammatory effects for Ceylon cinnamon, hops, and their major compounds. In a second approach, we then searched for clinical studies testing the efficacy of the plants in treating human disease.