3- O-Methyl- d-galactose residues in lycophyte primary cell walls

Abstract

Acid hydrolysis of cell wall-rich material from young leaves of the lycophyte Selaginella apoda (L.) Spring yielded substantial amounts of 3- O-methyl- d-galactose ( 1) in addition to the usual major monosaccharides (glucose, galactose, arabinose, xylose and galacturonic acid). The yield of 1 approximately equalled that of galacturonic acid. Compound 1 was identified as 3- O-methylgalactose by its 1H and 13C NMR spectra, and shown to be the d-enantiomer by its susceptibility to d-galactose oxidase. Compound 1 was detected in acid hydrolysates of the alcohol-insoluble residues from young leaves of all lycophytes tested, both homosporous ( Lycopodium, Huperzia and Diphasiastrum) and heterosporous ( Selaginella). It was not detectable in the charophyte green algae Coleochaete scutata, Chara coralina or Klebsormidium flaccidum, any bryophytes [a hornwort ( Anthoceros), four liverworts and three mosses], or any euphyllophytes [a psilopsid ( Psilotum), a horsetail ( Equisetum), eusporangiate and leptosporangiate ferns, the gymnosperm Gnetum, and diverse angiosperms]. A high content of 1 is thus an autapomorphy of the lycophytes.