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.
Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, People's Republic of China, 201203.
Jinyou
J
Duan
Yun
Y
Zheng
Qun
Q
Dong
Jinian
J
Fang
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