Several structurally different glucans were characterized as components of Ramalina celastri. Aqueous KOH extraction of the lichen at 100°C, followed by dialysis provided amylose (0.02%), identified and quantified by its blue coloration with iodine. The extract was frozen and thawed and the resulting precipitate (2% yield) shown to be a mixture of two insoluble D-glucans, with (1→3)- and (1→3),(1→4)-linkages, respectively, as shown by 13C NMR spectroscopy. On treatment with 0.5% aqueous NaOH at 50°C, the material which remained insoluble was a linear β-glucan with regularly distributed (1→3)- and (1→4)-linkages in a 1:1 molar ratio (nigeran, 1.2% yield), whereas that which solubilised was a linear β-glucan with (1→3)-linkages (laminaran, 0.8% yield). The mother liquor of the KOH extraction was treated with Fehling solution to give a precipitate and the supernatant contained an α-D-glucan (28% yield) with (1→3)- and (1→4)- linkages in a molar ratio of 3:1, and which were distributed irregularly. The structures of these two (1→3),(1→4)-linked β-glucans were characterized by methylation, controlled Smith degradation and 13C and 1H NMR spectroscopic analyses.

β-D-glucan, α-D-Glucans, amylose, Ramalina celastri

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
	bDGlcp	103.2	73.2	86.4	68.7	76.6	61.1


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
	bDGlcp	4.61	3.38	3.58	3.33	3.34	3.54-3.78


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
	bDGlcp	103.2/4.61	73.2/3.38	86.4/3.58	68.7/3.33	76.6/3.34	61.1/3.54-3.78

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@@H]1[C@@H](O)[C@H](*)O[C@H](CO)[C@H]1O

162.141 g/mol (C₆H₁₀R₂O₅, R = next and previous repeats, not counted in mol weight)