Certain members of the Coronaviridae family have emerged as zoonotic agents and
have recently caused severe respiratory diseases in humans and animals, such as SARS, MERS,
and, more recently, COVID-19. Antivirals (drugs and antiseptics) capable of controlling viruses at
the site of infection are scarce. Microalgae from the Chlorellaceae family are sources of bioactive
compounds with antioxidant, antiviral, and antitumor activity. In the present study, we aimed to
evaluate various extracts from Planktochlorella nurekis in vitro against murine coronavirus-3 (MHV-3),
which is an essential human coronavirus surrogate for laboratory assays. Methanol, hexane, and
dichloromethane extracts of P. nurekis were tested in cells infected with MHV-3, and characterized
by UV-vis spectrophotometry, nuclear magnetic resonance (NMR) spectroscopy, ultraperformance
liquid chromatography-mass spectrometry (UPLC-MS), and the application of chemometrics through
principal component analysis (PCA). All the extracts were highly efficient against MHV-3 (more than
a 6 Log unit reduction), regardless of the solvent used or the concentration of the extract, but the
dichloromethane extract was the most effective. Chemical characterization by spectrophotometry
and NMR, with the aid of statistical analysis, showed that polyphenols, carbohydrates, and isoprene
derivatives, such as terpenes and carotenoids have a more significant impact on the virucidal potential.
Compounds identified by UPLC-MS were mainly lipids and only found in the dichloromethane
extract. These results open new biotechnological possibilities to explore the biomass of P. nurekis; it is
a natural extract and shows low cytotoxicity and an excellent antiviral effect, with low production
costs, highlighting a promising potential for development and implementation of therapies against
coronaviruses, such as SARS-CoV-2.
