C-glucosidic ellagitannins from lythri herba (European Pharmacopoeia): Chromatographic profile and structure determination

Article abstract of DOI:10.1002/pca.2415

Introduction Lythri herba, a pharmacopoeial plant material (European Pharmacopoea), is obtained from flowering parts of purple loosestrife (Lythrum salicaria L.). Although extracts from this plant material have been proven to possess some interesting biological activities and its pharmacopoeial standardisation is based on total tannin content determination, the phytochemical characterisation of this main group of compounds has not yet been fully conducted. Objective To isolate ellagitannins from Lythri herba, determine their structures and develop chromatographic methods for their qualitative analysis. Results Five C-glucosidic ellagitannins - monomeric- vescalagin and castalagin together with new dimeric structures - salicarinins A-C, composed of vescalagin and stachyurin, vescalagin and casuarinin, castalagin and casuarinin units connected via formation of valoneoyl group, were isolated using column chromatography and preparative HPLC. Structures were determined according to ¹H and ¹³C-NMR (one- and two-dimensional), electrospray ionisation-time of flight (ESI-TOF), electrospray ionisation-ion trap (ESI-MSⁿ) and circular dichroism (CD) spectra, together with acidic hydrolysis products analysis. HPTLC on RP-18 modified plates and HPLC-DAD-MSⁿ on RP-18 column methods were developed for separation of the five main ellagitannins. Copyright 2012 John Wiley & Sons, Ltd. Composition of ellagitannins in Lythri herba (European Pharmacopoeia) was examined. Five C-glucosidic ellagitannins were isolated: monomeric vescalagin and castalagin together with not previously reported dimeric salicarinins A-C composed of vescalagin and stachyurin, vescalagin and casuarinin, castalagin and casuarinin units connected via formation of the valoneoyl group. Structures were determined according to ¹H- and ¹³C-NMR (one- and two-dimensional), ESI-TOF, MSⁿ and CD spectra together with acidic hydrolysis products analysis. HPLC-DAD-MSⁿ and HPTLC methods were developed for qualitative determination of ellagitannins in the examined plant extract. Copyright