Lichenan lichen

Lichen consists of mainly of the polysaccharide lichenan, with some for 62% of the total carbohydrate content. Lichenan is a linear polysaccharide from /3-D-glucopyranose that is linked by both 1,3 and 1,4 linkages (37). 

Baron M, lacomini M, Fanta ES, Gorin PA (1991) Galactomannan, lichenan and, isolichenan from the polysaccharide-rich lichen Neuropogon aurantiaco-ater. Phytochemistry 30 3125-3126... 

Nishikawa Y, Yoshimoto K, Horiuchi R (nee Murakami), Michishita K, Okabe M, Fukuoka F (1979) Studies on the water-soluble constituents of lichens. III. Changes in antitumor effect caused by modifications of pustulan- and lichenan-type glucans. Chem Pharm Bull 27 2065-2072... 

Lichens have proven a useful source of antiviral agents. Established antiviral properties have been attributed to some specific lichen secondary metabolites including usnic acid, parietin, anthraquinones, hypericin, lichenan, etc. For instance, lichenan, which is widely distributed in lichens, is demonstrated to inhibit the tobacco mosaic vims (Stubler and Buchenauer 1996). 

Several lichens Lichenan Tobacco mosaic virus Stabler and Buchenauer (1996)... 

Nishikawa, Y., K. Yoshimoto, R. Horiuchi (nee Murakami), K. Michishita, M. Okabe, and F. Fukuoka Change in Antitumor Effect Caused by Modifications of Pustulan Type and Lichenan Type Glucans. Chem. Pharm. Bull. (Japan) 27,1065 (1979). Nolan, T. J., J. Algar, E. P. McCann, W. A. Manahan, and N. Nolan The Chemical Constituents of Lichens Found in Ireland. Buellia canescens. Part 3. The Constitution of Diploicin. Sci. Proc. Roy. Dublin Soc. 24, 319 (1948). 

A sulfate prepared by chlorosulfonation of GE-3-, a partially acetylated P—(I 6) glucan of the lichen Umbilicaria esculenta, inhibited the cytopathic effect of human inununodeficiency virus (HIV) and suppressed the HlV-antigen expression in Molt-4 (clone 8) cells (371). Emodin, 7-chloroemodin, 7-chloro-l-O-methylemodin and 5,7-dichloroemodin have exhibited antiviral activity 738, 72). Stiibler et al. 675,676) investigated the antiviral activity of the glucan lichenan. Seventeen depsides and depsidones have been examined for their inhibitory activity against HIV integrase 559). Yamamoto et al. 743) tested the extracts of numerous lichens on their inhibition of Epstein-Barr virus activation. 

The lichen Cetraria islandica (Iceland moss) contains the structural polysaccharide lichenan, which is insoluble in cold water, and the related water-soluble polysaccharide isolichenan. Periodate oxidation and methylation studies indicate that lichenan is a linear glucan containing both / -D-(i - 3) and /S-D-(i 4) linkages in a ratio approximately 2 5, while isolichenan is similarly constituted but with the linkages in the ratio 3 2. Isolichenan has a TTP of 42-44. 

Some secondary metabolites of lichens were also reported to have antiviral effects. Perry and coworkers in 1999 reported the antiviral activity of ( )-usnic acids (50 and 51) against the Poho and Herpes simplex type 1 viruses [63]. The viricidal activity of parietin (3), a secondary metabolite of Teloschistes chrysophthalmus (L.) Th. Fr., was reported against Junin and Tacaribe arena viruses [85]. Tobacco mosaic virus inhibition potential of lichenan (73), a metabolite of many lichens, was also reported in the literature [86]. Usnic acid (50) was also reported to exhibit activity against same viruses as tested for parietin (3) [6] (Table 3). 

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