Procyanidins from Myrothamnus flabellifolia

Abstract

From the ethyl acetate soluble fraction of an acetone–water extract of the twig tips of Myrothamnus flabellifolia Welw. (Myrothamnaceae), a variety of flavan-3-ols (epicatechin, epigallocatechin and their 3-O-galloylated analogues) and procyanidins (DP ≤ 3) were isolated and identified for the first time: Procyanidin B3 [catechin-(4α → 8)-catechin], B4 [catechin-(4α → 8)-epicatechin], B6 [catechin-(4α → 6)-catechin] and catechin-(4α → 8)-epigallocatechin along with the galloylated analogues B4-3′-O-gallate, procyanidin B2-3′-O-gallate [epicatechin-(4β → 8)-epicatechin-3-O-gallate], B2-3,3′-di-O-gallate, procyanidin B5-3,3′-O-gallate [epicatechin-3-O-gallate-(4β → 6)-epicatechin-3-O-gallate], catechin-(4α → 8)-epigallocatechin-3-O-gallate, the trimer procyanidin C1-3″-O-gallate[epicatechin-(4β → 8)-epicatechin-(4β → 8)-epicatechin-3-O-gallate] and the new epicatechin-3-O-gallate-(4β → 6)-epicatechin-3-O-p-hydroxybenzoate. The structures were elucidated by 1D- and 2D-NMR experiments of their peracetylated derivatives, partial acid-catalysed degradation with phloroglucinol, ESI-MS and CD spectra.

Keywords:

• Myrothamnus flabellifolia
• Myrothamnaceae
• Procyanidins
• Flavan-3-ols

Acknowledgements

Financial support by Myro AG, Greifensee, Switzerland and valuable discussions with Dr R. Plüss are acknowledged. The authors thank Dr Bergander, Dr Lahl and Ms Heim, Münster for recording NMR spectra. Thanks are also due to Dr Luftmann and Mr Meiners, Münster for MS measurements, to Mr Klaes for providing assistance with measuring CD-values and Ms Liefländer-Wulf and Ms Krug for skilful technical assistance.