The
coronavirus disease 2019 (COVID-19) pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite the development of
vaccines, the emergence of SARS-CoV-2 variants and the absence of effective
therapeutics demand the continual investigation of
COVID-19. Natural products containing active ingredients may be good therapeutic candidates. Here, we investigated the effectiveness of
geraniin, the main ingredient in medical plants Elaeocarpus sylvestris var. ellipticus and Nephelium lappaceum, for treating
COVID-19. The
SARS-CoV-2 spike protein binds to the human
angiotensin-converting enzyme 2 (hACE2) receptor to initiate virus entry into cells; viral entry may be an important target of
COVID-19 therapeutics.
Geraniin was found to effectively block the binding between the
SARS-CoV-2 spike protein and hACE2 receptor in competitive
enzyme-linked
immunosorbent assay, suggesting that
geraniin might inhibit the entry of SARS-CoV-2 into human epithelial cells.
Geraniin also demonstrated a high affinity to both
proteins despite a relatively lower equilibrium dissociation constant (KD) for the spike
protein (0.63 μM) than hACE2 receptor (1.12 μM), according to biolayer interferometry-based analysis. In silico analysis indicated
geraniin's interaction with the residues functionally important in the binding between the two
proteins. Thus,
geraniin is a promising therapeutic agent for
COVID-19 by blocking SARS-CoV-2's entry into human cells.