Structural analysis of a pectic polysaccharide from the leaves of Diospyros kaki.
A pectic polysaccharide DL-2A with a molar mass of 8.5 x 10(5), was obtained from the boiling water extract of Diospyros kaki leaves. It had [alpha]20D -21.8 degrees (c 0.22, H2O) and consisted of rhamnose, arabinose, galactose, xylose and galacturonic acid units in the molar ratio of 0.4:3.4:2.4:1.0:0.8, along with traces of glucuronic acid. About 16.7% of galacturonic acid existed as the methyl ester. A combination of linkage analyses, periodate oxidation, partial acid hydrolysis, selective lithium-degraded reaction, ESIMS, 1H- and 13C- NMR spectral analyses revealed its structural features. It was found that DL-2A possessed an alpha-(1-->4)-galacturonan backbone with some insertions of alpha-1,2-Rhap residues. The side-chains of arabino-3,6-galactan were attached to the backbone via O-4 of Rhap residues and O-3 of GalAp residues, while 4-linked xylose residues (forming short linear chains) were directly linked to O-4 of rhamnose residues, not as part of the xylogalacturonan. These novel structural features enlarge the knowledge on the fine structure of pectic substances in the plant kingdom.
Duan
Jinyou
J
Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, People's Republic of China, 201203.
Zheng
Yun
Y
Dong
Qun
Q
Fang
Jinian
J
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D029788:Diospyros / Q000737:chemistry*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010368:Pectins / Q000737:chemistry* / Q000302:isolation & purification; D018515:Plant Leaves / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
D010368:Pectins