Antiviral flavonoid from Pterocaulon sphacelatum, an Australian Aboriginal medicine.

The antipicornaviral activity of an ethanolic extract of the green aerial parts of the Australian plant Pterocaulon sphacelatum (Labill.) Benth. & Hook. f. ex F. Muell. has been investigated. This plant has been a favoured traditional medicine, used for the treatment of colds by the Australian Aboriginal people. Antiviral activity-guided fractionation of the extract of P. sphacelatum using an inhibition of poliovirus-induced cytopathic effect assay, has yielded the antiviral flavonoid chrysosplenol C (3,7,3'-trimethoxy-5,6,4'-trihydroxyflavone). This compound is a 4'-hydroxy-3-methoxyflavone, one of a group of compounds known to be potent and specific inhibitors of picornaviral replication. These compounds inhibit the replication of rhinoviruses, the most frequent causative agent of the common cold. The coumarin 6,7,8-trimethoxycoumarin was also isolated from the ethanolic extract.