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|a In this study, polysaccharides from Xanthoria parietina, a wide spread lichen
from central Europe, were isolated, purified and analyzed concerning the
structural features, in combination with functional investigation of the influence
on ,?1urine macrophage cell line RAW264.7 in vitro.
Defatted dried lichen (140 g, WT) was submitted to consecutive cold water (4°C,
12 h), freezing (-20°C) and thawing (room temperature), hot water (100°C) as
well as alkaline (0.5: M aq. NaOH) extractions (each in triplicate). Only hot
aqueous extract, XH (2.8%, W/WT) was further fractionated by ion exchange
chromatography to yield mainly H-1 (0.7%) and H-2 (0.4%) (W/WT) fractions.
Chromatographic purification of the fractions by gel permeation
chromatography yielded polysaccharides H-1-3 (0.39%) and H-2-1 (0.07%)
(W/WT) with molecular weights Mwof 13.7 and 525 kDa respectively, prior to
ethanol precipitation, dialysis and lyophilisation.
Monomers composition analysis by HPAEC-PADand GC-MSrevealed that H-1-3
consisted mainly of glucose (> 98%), while H-2-1 was composed of man nose
(74.3%), galactose (14.1%), glucose (9.8%) and rhamnose (1.8%) as well as
trace of arabinose. O-/L-configuration of diastereomers analyzed by capillary
zone elactrophoresis (CZE) as well as the anomeric configuration by lH- and 13CNMR
indicated the presence «-0- glucose in H-1-3 and c-D-manncse, «-0-
galactose, u-D-glucose and c-t-Rhap in H-2-1. Subsequently, linkage sequences
were determined by GC-MS analysis of partially methylated alditol acetates,
nano-ESI QTOF-MS/MS analysis of oligosaccharides and 2D-NMR analysis of
native polysaccharides and oligosaccharides. In nano-ESI-Q- TOF MS/MS
analysis, the use of silver adducts in positive-ion mode settings was established
and found to be capable of rising A- and X-type fragment ions generated from
cross-ring cleavages, together with the rise of 8- and Y-type ions from the
glycosidic bonds cleavages of the oligosaccharides prepared from H-1-3 but not
H-2-1. For H-2-1, the use of chloride adduct in negative-ion mode settings was
better capable in rising similar type of fragment ions.
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