Structural characterisation of novel lichen heteroglycans by NMR spectroscopy and methylation analysis.
Two galactofuranomannans, Ths-4 and Ths-5, were isolated from the lichen, Thamnolia vermicularis var. subuliformis, using ethanol fractionation and anion-exchange and size-exclusion chromatography. The average molecular weights of Ths-4 and Ths-5 were estimated to be 19 and 200 kDa, respectively. Structural characterisation of Ths-4, Ths-5 and their partially hydrolysed derivatives was performed by methanolysis and methylation analysis. The intact and partially hydrolysed Ths-4 was further analysed using NMR spectroscopy (1D, COSY, NOESY, TOCSY, HSQC and HMBC). According to the data obtained, the heteroglycans Ths-4 and Ths-5 have similar structures, but have large differences in molecular weight. The structure is composed of 3-O-linked and 5-O-linked galactofuranosyl chains linked to a mannan core. The mannan core consists of a main chain of alpha-(1-->6)-linked mannopyranosyl residues, substituted at O-2 with either a single alpha-mannopyranosyl unit or an alpha-Manp-(1-->2)-alpha-Manp-(1-->2)-alpha-Manp group in the ratio of approximately 1:3, respectively. The polysaccharides have idealised repeating blocks as is shown.
Omarsdottir
Sesselja
S
University of Iceland, Faculty of Pharmacy, Hagi, Hofsvallagata 53, IS-107 Reykjavik, Iceland.
Petersen
Bent O
BO
Paulsen
Berit Smestad
BS
Togola
Adiaratou
A
Duus
Jens Ø
JØ
Olafsdottir
Elin S
ES
D002852:Chromatography, Ion Exchange; D005936:Glucans / Q000737:chemistry*; D008011:Lichens / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D028321:Plant Preparations / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification
D005936:Glucans; D028321:Plant Preparations; D011134:Polysaccharides