PROS1 and infection: Moreover, it was reported that baicalin can suppress angiotensin-converting enzyme 2 (ACE2) activity to inhibit the attachment of SARS-CoV spike protein (S protein) to ACE2, which was the entrance of SARS-CoV-2 into host cells via S protein, reducing infections (Yang et al., 2020; Boozari and Hosseinzadeh, 2021).