Studies on the polysaccharides having activity on the reticuloendothelial system from several Oriental crude drugs

Eleven polysaccharides have been isolated from the hot water extracts of several Oriental crude drugs. They showed remarkable reticuloendothelial system (RES)-potentiating activity. The effect of the polysaccharides on the RES was demonstrated by a modification of the in vivo carbon clearance test using ICR-SPF male mice. Structural features of the immunologically active polysaccharides were elucidated by chemical and spectral procedures. Saposhnikovans A, B, and C were obtained from the roots and rhizomes of Saposhnikovia divaricata. The ''A'' has α-1→4-linked D-galacturonan backbone bearing α-1→5-linked L-arabino-β-3,6-branched D-galactan side chains, and the ''C'' possesses a pectin-like rhamnogalacturonan backbone carrying α-3,5-branched L-arabinan and β-3,4-branched D-galactan side chains. A neutral polysaccharide (MVS-I) and two acidic polysaccharides (MVS-IIIA and -IVA) were isolated from the seeds of Malva verticillata. MVS-I has a backbone consisting of β-1→3-linked D-glucan and D-galactan bearing α-1→5-linked L-arabinan and β-1→4-linked D-galactan side chains. The basic structure of both MVS-IIIA and MVS-IVA consists of α-1→5-linked L-arabino-β-3,6-branched D-galactan. In addition, both the substances have 1→3-linked L-arabinopyranosyl residues with β-1→4-linked D-xylan and α-1→4-linked D-galacturonan units. An arabinoxylan, named cinnaman AX, was obtained from the barks of Cinnamomum cassia. It possesses β-1→4-linked D-xylan backbone carrying side chains composed of both α-L-Araf-(1→3)-β-L-Arap and α-L-Araf-(1→4)-β-D-Xylp-(1→3)-β-L-Arap units at position of 3 of ca. 70 % of xylose residues. The rhizomes of Curcuma longa afforded four highly active substances, named ukonans A, B, C, and D. These polysaccharides have a common structural unit of α-L-arabino-β-3,6-branched D-galactan with α-1→3-linked L-arabinopyranosyl residues, β-3,4-branched D-xylan, α-1→4-linked D-glucan, and rhamnogalacturonan units. Deacetylated product of Plantago-mucilage A, the mucous polysaccharide isolated from the seeds of Plantago asiatica, also showed remarkable activity. This substance has β-1→4-linked D-xylan backbone bearing side chains composed of ̄-D-Xylp and of α-D-GlcpA-(1→3)-α-L-Araf at position 3.