Polyphenolic metabolites of Epilobium hirsutum

Abstract

Evaluation of the constitutive polyphenolics of the whole plant extract of Epilobium hirsutum was carried out by reverse-phase HPLC. The unique ellagitannins, 2- O-galloyl 3- O-valoneoyl dilactone-(α/β)- 4C 1-glucopyranose, 1′-monodecarboxyvaloneic acid dilactone and valoneic dilactone dioxine were isolated and characterized. The known polyphenolics, gallic, protocatechuic, ellagic, valoneic dilactone and p-coumaric acids, methyl gallate, p-methoxy gallic acid methyl ester, 6- O-galloylglucose, 1,6-di- O-galloylglucose, 2,3-di- O-galloylglucose, 1,2,6-tri- O-galloylglucose and the 3- O-glucuronides, 3- O-arabinosides and 3- O-rhamnosides of kaempferol, quercetin and myricetin, their free aglycones 3- O-galactoside and quercetin and myricetin were also identified. The structures were established by conventional methods of analysis and confirmed by 1H, 13C NMR and negative ESI-mass spectrometry. 2D-long range selective proton decoupling and chemical shift correlation NMR experiments were applied for the new polyphenolics. The HPLC phenolic profile was used for the quality assessment of the E. hirsutum extract for medicinal purposes and also as a fingerprint for the authentication of the plant material.