Synthesis and Anti-influenza Activity of Novel Thiadiazole, Oxadiazole and Triazole Based Scaffolds

Background: Influenza is a common respiratory tract infection caused by RNA-virus of the family Orthomyxoviridae; influenza virus, causing variety of symptoms including fever, nasal secretions, cough, muscle pain and pneumonia. It is classified into three distinct types A, B & C. Many 1,3,4-thiadiazoles, 1,3,4-oxadiazoles and 1,2,4-triazoles have showed broad spectrum of biological activities. These heterocycles are considered lead for their high antiviral activity against wide range of viruses. Methods: Research and online content related to chemistry of anti-influenza agents have been reviewed, five schemes were applied to obtain the target compounds, then these compounds underwent in vitro anti-influenza screening. Results: Thirty novel compounds were in vitro screened against the highly pathogenic avian influenza H5N1 virus in MDCK cells. Amantadine was used as control drug. Six compounds showed excellent activity (79-100% virus inhibition) namely 6c, 14b, 14c, 19b, 30b, 30e with 14c being the most active compound. Five compounds exhibited moderate inhibition (44-70%) namely 5c, 6b, 23a, 23b, 30c. Conclusion: From the previous results, we found that presence of the triazole ring decreased the antiviral activity. While compound 19b that contains benzimidazole nucleus showed excellent inhibition. Presence of the thiadiazole ring greatly affected the activity in different ways according to the substitution on the ring. Moving to the oxadiazole series 14a-c, 16, 28b, c and 30a-f, the change in substitutions greatly affected the antiviral activity. Presence of 4-tolyl or 4-chlorophenyl at position 5 of the oxadiazole greatly enhanced the activity in 14b, c.