Direct and specific inactivation of rhinovirus by chalcone Ro 09-0410

Studies of various analogs related to the antipicornavirus agent, 4',5-dihydroxy-3,3',7-trimethoxyflavone (Ro 09-0179), led to the identification of 4'-ethoxy-2'-hydroxy-4,6'-dimethoxychalcone (Ro 09-0410), a new and different type of antiviral agent. Ro 09-0410 had a high activity against rhinoviruses but no activity against other picornaviruses. Of 53 rhinovirus serotypes so far tested, 46 were susceptible to Ro 09-0410 in HeLa cell cultures. The concentration of Ro 09-0410 inhibiting 50% of the types of rhinovirus was about 0.03 micrograms/ml, whereas the 50% cytotoxic concentration was 30 microgram/ml. Ro 09-0410 inactivated rhinoviruses in direct dose-, time-, and temperature-dependent fashion. Since infectivity, reduced by exposure to the agent, completely regained the original level by extraction of the agent with chloroform, the inactivation may be associated with the binding of the agent to some specific site of the rhinovirus capsid.