Comparative studies of the polysaccharides isolated from lichenized fungi of the genus Cladonia: significance as chemotypes

Abstract

β- D-Glucans of the laminaran type were prepared from 15 Cladonia spp., Cladonia bellidiflora, Cladonia boryi, Cladonia clathrata, Cladonia connexa, Cladonia crispatula, Cladonia furcata, Cladonia gracilis, Cladonia ibitipocae, Cladonia imperialis, Cladonia miniata, Cladonia penicillata, Cladonia salmonea, Cladonia signata, Cladonia substellata and Cladonia uncialis. They were extracted with 10% aqueous KOH at 100°C, giving polysaccharides with varying yields and proportions of mannose, galactose and glucose. Their aqueous solutions were freeze–thawed giving precipitates of mixed α-glucan (nigeran) and β-glucans, which were isolated and suspended in aqueous 0.5% KOH at 50°C, which preferentially dissolved the β-glucan. In the case of the C. uncialis product, it was subjected to methylation analysis, which gave rise to 2,4,6-tri- O-methylglucitol acetate only, corresponding to (1→3)-linkages. Its specific rotation (+4°) and one- and two-dimensional nuclear magnetic resonance (NMR) spectra were consistent with β-linkages. 13C and 1H-1 signals were observed, respectively, at δ 102.8 (C-1), 86.0 (C-3), 76.2 (C-5), 72.6 (C-2), 68.3 (C-4) and 60.7 (C-6), and 4.55 (H-1), 3.31 (H-2), 3.49 (H-3), 3.27 (H-4), 3.27 (H-5), 3.48 (H-6) and 3.72 (H-6′). Similar 13C-NMR spectra were obtained from the glucans from the other 14 Cladonia spp. The β- D-glucans of the laminaran type seems to be present in all Cladonia spp. being significant for chemotyping since it was observed in every species studied.