Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/18388
The lichen heteroglycan thamnolan, from the whiteworm lichen (Thamnolia subuliformis), has previously been shown to have a unique structure among other lichen polysaccharides. The heteroglycan is composed of long galactofuranosyl chains and a rhamnopyranosyl core. A related lichen species has been used historically in folk medicine and thamnolan‘s immunomodulating bioactivity has been demonstrated in other studies. Thamnolan‘s unique structure may play an important role in its bioactivity and although its structure has been described to a large extent, its structure has not been conclusively confirmed.
The objective of this research project was to extract, isolate and purify thamnolan from whiteworm lichen and then analyze its structure. Extraction and isolation was achieved using hot aqueous extraction of the lichen, ethanol fractionation, dialysis, lyophilization, ion exchange chromatography and gel filtration. A sample of the purified Fraction III-a-1 (thought to be thamnolan) was analyzed using methanolysis and gas chromatography (GC) and methylation and GC-MS analysis to discern its monosaccharide ratios and linkage types. Methanolysis revealed Fraction III-a-1 to contain monosaccharides in a ratio of 3.2:25.3:7.0:3.5:50.0:11.0. The mean molecular weight of Fraction III-a-1 was determined using size exclusion chromatography on two different columns and was determined to be 1420 kDa or 1260 kDa. The obtained values from these analyses were then compared to known values from previous studies of thamnolan. These studies showed thamnolan to have a mean molecular weight of 1450 kDa and a monosaccharide composition in a ratio of rha/xyl/man/gal/glc 27:8:4.5:49:12.5. The results of this extraction should therefore be considered consistent with previous studies and point to thamnolan‘s successful extraction. However, in order to confirm its detailed structure, partial hydrolysis and 1D and 2D NMR analysis is required.