Synthesis and iNOS inhibitory activities of thioflavones

A number of thioflavones has been synthesized and evaluated for their iNOS inhibitory activities. Thiowogonin (6) was obtained from naturally occurring chrysin in 5 steps. Other thioflavones were prepared from the corresponding flavones in a single step by the reaction with Lawesson's reagent. The biological activities of thioflavones were not enhanced by the functional group conversion from carbonyl to thiocarbonyl. Compounds 11 and 13 showed potent NO inhibitory activity at high concentration (40 uM), leading to the possible development of novel neuroprotective agents based on wogonin.