*4.2. Studied Formulations*

Echinochrome A (Ech, 2,3,5,7,8-pentahydroxy-6-ethyl-1,4-naphthoquinone) 98.0%, pharmaceutical, state registration number PN002362/01-2003, G.B. Elyakov Pacific Institute of Bioorganic Chemistry FEB RAS, Russia.

Ascorbic acid (Asc) 99.8%, pharmaceutical, AppliChem, Germany. α-Tocopherol (Toc) ≥96%, pharmaceutical, Carl Roth, Germany. The composition of antioxidants Ech + Asc + Toc at the weight ratio of 5:5:1. The composition containing Asc and Toc at the weight ratio of 5:1. Ribavirin®, pharmaceutical, Vertex, Russia. Acyclovir®, pharmaceutical, Belmedpreparation, Republic of Belarus.

The tested formulations were dissolved in dimethylsulfoxide (DMSO, Sigma, Saint-Louis, MO, USA) and stored at −20 ◦C. The stock solutions (10 mg/mL) of formulations were diluted with a suitable cell culture medium so that the final concentration of DMSO was 0.5%.
