RHAMNOGALACTURONAN-II FROM THE LEAVES OF PANAX-GINSENG MEYER,C.A. AS A MACROPHAGE FC-RECEPTOR EXPRESSION-ENHANCING POLYSACCHARIDE

A complex pectic polysaccharide (GL-4IIb2) has been isolated from the leaves of Panax ginseng C.A. Meyer, and shown to be a macrophage Fc re ceptor expression-enhancing polysaccharide. The primary structure of G L-4IIb2 was elucidated by composition, H-1 NMR, methylation, and oligo saccharide analyses. GL-4IIb2 consisted of 15 different monosaccharide s which included rarely observed sugars, such as 2-O-methylfucose, 2-O -methylxylose, apiose, 3-C-carboxy-5-deoxy-L-xylose (aceric acid, AceA ), 3-deoxy-D-manno-2-octulosonic acid (Kdo), and 3-deoxy-D-lyxo-2-hept ulosaric acid (Dha). Methylation analysis indicated that GL-4IIb2 comp rised 34 different glycosyl linkages, such as 3,4-linked Fuc, 3- and 2 ,3,4-linked Rha, and 2-linked GlcA, which are characteristic of rhamno galacturonan II (RG-II). Sequential degradation using partial acid hyd rolysis indicated that GL-4IIb2 contained alpha-Rhap-(1 --> 5)-Kdo and Araf-(1 --> 5)-Dha structural elements, an AceA-containing oligosacch aride, and uronic acid-rich oligosaccharide chains in addition to an a lpha-(1 --> 4)-galacturono-oligosaccharide chain. FABMS and methylatio n analyses suggested that the AceA-containing oligosaccharide was a no nasaccharide in which terminal Rha was additionally attached to positi on 3 of 2-linked Arap of the octasaccharide chain observed in sycamore RG-II. Component sugar and methylation analyses assumed that the uron ic acid-rich oligosaccharides possessed a similar structural feature a s those in sycamore RG-II. GL-4IIb2 had a larger molecular mass (11,00 0) than sycamore RG-II(similar to 5000). (C) 1997 Elsevier Science Ltd .