Studies on the metabolism of the Chrysophyceae. Comparative structural investigations on leucosin (chrysolaminarin) separated from diatoms and laminarin from the brown algae

Abstract

Crystalline chrysolaminarin separated from a mixture of diatoms (Chrysophyceae) had m.p. 273[degree] [[alpha]]D-6[degree]and was shown to contain 99-5% of glucose. Chromatographic examination of total hydrolysates of laminarin and of chrysolaminarin revealed the presence of mannitol in the former but not in the latter. The alcohols obtained on reduction of the polysaccharides with borohydride gave on hydrolysis glucose, sorbitol and mannitol from laminarin and glucose and sorbitol from chrysolaminarin. 2:3:4:6-Tetra-O-methylglucose, and di-O-methylglucose in the ratio of 1:10.5:0.46 and 1:16:0.6 were , present in the hydrolysates of methylated chrysolaminarin and laminarin respectively. The presence of the di-O-methyl sugar indicates the possible presence of one branch point per molecule. The methylated sugars were separated on thick paper and evidence was obtained that both tri-O-methyl fractions consisted of a mixture of 2:4:6- and 2:3:4-tri-O-methylglucoses, in the ratio of about 11:1 and 15:1 in chrysolaminarin and laminarin respectively. This provides proof of the presence of 1:6[image]-linkages in the linear 1:3[image]-linked chains. The amount of periodate reduced by both polysaccharides is in agreement with the presence of a high proportion of l:3[image]-linked glucose units. The quantity of formaldehyde released by laminarin and chrysolaminarin and their respective alcohols on oxidation with periodate confirms the presence of mannitol-terminated chains (M-chains) in laminarin. No evidence of M-chains in chrysolaminarin could be obtained. The degree of polymerization of both polysaccharides calculated from formaldehyde release is about 21 glucose units. The incomplete oxidation of the two polysaccharides under conditions which facilitate degradation of 1:3[image]-linked glucose chains provides confirmation of the presence of 1:6[image]-linked units in chrysolaminarin and of similar linkages of M-chains or both in laminarin.