Aloin B (Isobarbaloin) is an orally active SARS-CoV-2 papain-like protease (PLpro) inhibitor with an IC50 of 16.08 μM (hydrolytic activity) and 17.51 μM (deubiquitinase activity). Aloin B is metabolized by rat intestinal flora into aloe-emodin-9-anthrone