The anthraquinones are a huge group of natural compounds, and one of the compounds from that group is 1,8-dihydroxy-3-methoxy-6-methyl-anthracene-9,10-dione (parietin, known as physcion as well). The parietin is produced by various plants such as R. crispus and R. japonicus Houtt., as well as many fungi such as Aspergillus spp., Penicillium spp., and Alternaria spp. It is well known that parietin possesses antitumor activity, antioxidant activity, antimutagenic activity, topoisomerase II inhibitory activity, in vitro antiviral activity against poliovirus, and antifungal activity. Knowing these facts it can be supposed that they can found application in medicinal chemistry. A study was conducted to explore the antioxidative and inhibitory potency of parietin. Density functional theory (DFT) is a powerful tool used for examining the antioxidative mechanisms. The Gaussian 09 program package is used to perform all electronic calculations. The equilibrium geometries of the parent molecule of parietin, its radical cation, radicals, and anions are calculated using the B3LYP-D3BJ functional in conjunction with the 6-311++G(d,p) basis set. The influence of water as a polar solvent (ε = 78.36) was estimated using the CPCM solvation model. Inhibitory potency of parientin is estimated by applying molecular docking simulations. For this purpose AutoDock 4.0 software is used, and inhibitory potency of parietin is estimated toward main protease M^pro from SARS-CoV-2.