tailieunhanh - Structural analysis of carrageenan extracted from kappaphycus alvalezii in Ninh Thuan province

Structure of carrageenan extracted from kappaphycus alvalezii was elucidated. Here, 1D and 2D NMR, including 1 H, 13 C, DEPT, 1 H- 1 H COSY, 1 H- 1 H TOCSY and HMQC, were performed to determine the structure of galactopyranosyl residues. Electrospray ionization spectrometry (ESIMS) was used to determine chair sequence of the polysaccharide. | Journal of Chemistry Vol. 44 4 P. 500 - 504 2006 STRUCTURAL ANALySIS OF CARRAGEENAN EXTRACTED FROM KAPPAPHYCUS ALVALEZII IN NINH THUAN PROVINCE Received 17 May 2005 THANH THI THU THUy TRAN THI THANH THUy Institute of Chemistry Vietnamese Academy for Science and Technology SUMMARy Structure of carrageenan extracted from kappaphycus alvalezii was elucidated. Here 1D and 2D NMR including 1H 13C DEPT 1H-1H COSY 1H-1H TOCSY and HMQC were performed to determine the structure of galactopyranosyl residues. Electrospray ionization spectrometry ESIMS was used to determine chair sequence of the polysaccharide. I - INTRODUCTION Carrageenans are sulfated polysaccharide extracted from the cell wall of red seaweed. The carrageenan family has three main branches named kappa k iota r and lambda À which are well differentiated by their gelling properties and protein reactivity 1 . All carrageenans have the common structural feature of being linear polysaccharides built up of alternating 1 3 linked P-D-galactopyranosyl and 1 4 linked a-D-galactopyranosyl units. Since their nontoxicity and characteristic properties carrageenans are applied to many fields of our daily life including food industry pharmaceutical industry and cosmetic-industry. In previous paper 2 we reported the experimental procedure of isolation and purification of carrageenan extracted from red seaweed Kappaphycus alvarezii in Ninh Thuan province of Vietnam and we proposed that this carrageenan is K-carrageenan which has an idealized chemical structure consisting of P- 1-3 -D-galactose-4-sulfate Galp4S G residue and a- 1-4 -3 6-anhydro-D-galactose AnGalp A residue repeating units as illustrated in figure. 500 Figure1 Idealized chemical structure of a disaccharide unit of K-carrageenan Earlier work 3 showed that the charged nature of the sugar units and their structural arrangement within the macromolecules render the carrageenans chemically highly reactive and account for their gelling property. On the basis of that