Cell wall polysaccharides from Mandevilla velutina (Apocynaceae) cultured cells:: extraction and chemical structure

Mandevilla velutina, a native plant to Brazil, is a source for bioactive triterpenoids which selectively and in a competitive way inhibited bradykinin (BK)-induced contractions of isolated rat uterus and guinea-pig ileum. These compounds were also found in cell cultures with an anti-BK action about two orders of magnitude larger than those from tuber extracts. Biomass from cell cultures was used to determine the basic composition of the cell wall, pursuing in further studies whether that parameter might be used to distinguish between cell lines and between cells of different ages. Hemicellulosic fractions showed a predominant neutral sugar composition, with D-Glc, L-Rha and D-Xyl as the major components. The deoxy-sugar L-Fuc was also found as a minor constituent. C-13 NMR spectrum of the hemicellulose A (5 M KOH) revealed beta and alpha conformations for D-Glc and L-Rha, respectively; the discrete signal for the carboxyl from the uronyl moiety (downfield), and the absence of (1-2) and (1-3) linkages. Spectroscopy also suggested a beta (1-6) linking for a polyglucose backbone or block. A more detailed structural analysis for the presence of L-Fuc is in progress. (C) 2000 Elsevier Science Ltd. All rights reserved.