Synthesis of some newer formazans and tetrazolium salts as antiviral agents.

Thirteen new formazans were prepared by the condensation of the phenylhydrazone of 3.4-dimethoxy-6-nitro-veratraldehyde with the appropriate phenyl diazonium salts. Attempts were made to oxidize these highly coloured formazans with various oxidizing agents to their corresponding tetrazolium salts. The most suitable oxidizing agent was found to be H2O2/Fe2+. Both the formazans and tetrazolium salts were screened for their antiviral activity against the Ranikhet disease virus and vaccinia virus in a stationary culture of chorioallantoic membrane of chick embryo. Among the 15 compounds tested one of the compounds namely 1-o-carboxyphenyl-3[3'.4'-dimethoxy-6'-nitrophenyl]-5-phenylformazan evinced 100% protection against the Ranikhet disease virus. Rest of the compounds showed significant protection ranging from 83 to 20%. An attempt has also been made to arrive at some structure-activity relationship.