Protogenkwanin, a new flavonoid from equisetum arvense L

Abstract From the fertile sprouts of Equisetum arvense L. have been isolated protogenkwanin 4'-glucoside and gossypitrin. The structure of protogenkwanin as 5-hydroxy-2-(1,4-dlhydroxy-2,5-cyclohexadienyl)-7-methoxy-4-chromenon is proved on the basis of chemical and physical evidence. It is demonstrated that articulatin a thiamine decomposing substance, from E. arvense , is identical with the known flavonol glycoside gossypitrin (= gossypetin-7-glucoside). The synthesis of 2,5-dihydroxy-2-(4 hydroxyphenyl)-7-methoxy-4-chromanon is reported.