Activity of Sesquiterpene Lactones and Umbelliferone From <i>Campovassouria cruciata</i> on SARS‐CoV‐2 Replication and on the Release of Pro‐Inflammatory Cytokines in Lung Cells

The investigation of natural products is a valid strategy to identify compounds active against coronaviruses. We herein report the screening of Baccharis and Campovassouria plant species against the murine betacoronavirus murine hepatitis virus-3 (MHV-3), assays that can be carried out in BSL-2 facilities. These genera occur exclusively in the Americas and are a source of secondary metabolites with antiviral and anti-inflammatory activity. Campovassouria cruciata emerged as the most active species from the screening, and its phytochemical investigation afforded the discovery of a new isomer of leptocarpin, 3-epi-leptocapin (1), in addition to the sesquiterpenes lactones leptocarpin (2) and arturin (3), along with umbelliferone (4). The structures were elucidated by extensive mono- and two-dimensional ¹H and ¹³C NMR data analysis. The antiviral activity of the isolated compounds was also assayed in Calu-3 cells infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). All compounds inhibited SARS-CoV-2 replication, with a reduction in viral load of approximately 1.7-2.0 log when tested at 7.5 µM. To evaluate potential anti-inflammatory activity, compounds were tested in A549 cells stimulated with IFN-γ and TNF-α. Both 3-epi-leptocarpin (1) and umbelliferone (4) inhibited interleukin-6 (IL-6) and IL-8 release significantly. Compound 1 reduced the production of reactive oxygen species (ROS) in A549 cells, as assessed by flow cytometry using DCFH-DA, whereas 4 exhibited ROS values seven-fold higher than the basal level. Our results highlight C. cruciata as a source of promising bioactive compounds, which deserve future investigations to explore their potential for the development of new therapeutic agents against inflammatory and viral diseases.