C-glucosidic ellagitannins from lythri herba (European Pharmacopoeia): Chromatographic profile and structure determination
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
Protecting-group-free solid-phase anchoring of polyphenolic C-glucosidic ellagitannins and synthesis of 1-alkylamino-vescalagin derivatives
The C-glucosidic ellagitannins vescalagin and vescalin are among the plant polyphenols that have been shown to interact with protein targets in a specific manner. This work describes a protecting-group-free method to immobilize these protein-binding natural products on a solid support, and a functionalizing cleavage method, which is adaptable to the solution-phase synthesis of vescal(ag)in derivatives, and which advantageously permitted the preparation of 1-alkylamino derivatives of vescalagin.
Tannins and Related Compounds. LI. Elucidation of the Stereochemistry of the Triphenoyl Moiety in Castalagin and Vescalagin, and Isolation of 1-O-Galloyl Castalagin from Eugenia grandis
The chirality of the nonahydroxytriphenoyl group in castalagin (1) and vescalagin (2) was determined to be in the S,S-series on the basis of circular dichroism analysis.In addition, a new ellagitannin (4) has been isolated from the leaves of Eugenia grandis (Myrtaceae), and the structure was established to be 1-O-galloyl castalagin on the basis of chemical and spectroscopic evidence. Keywords --- castalagin; vescalagin; C-glycosidic ellagitannin; atropisomerism; absolute stereochemistry; nonahydroxytriphenoyl group; flavogallonic acid; Eugenia grandis; 1-O-galloyl castalagin
Nonaka,Gen-Ichiro,Ishimaru, Kanji,Watanabe, Michiyo,Nishioka, Itsuo,Yamauchi, Tatsuo,Wan, Alfred S. C.
p. 217 - 220
(2007/10/02)
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