**6. Conclusion**

Polysaccharides from lichens unlike bacterial polysaccharides do not show a wide range of variation in sugar content. The predominant sugars are limited to glucose, galactose and mannose, with arabinose and xylose present in minor proportions in addition to others such as rhamnose. These polysaccharides however have been useful in chemotaxonomic studies due to this conservation of sugar structures and regular structural patterns. As far as biological activity is concerned, very few studies have been reported and it would be worthwhile further investigating the immunomodulating effects of the polysaccharides.
