Future directions in the study of pharmaceutical potential of lichens

Abstract

Lichens are a stable self-supporting symbiotic organism, composed of a fungal and an algal partner. In this symbiotic form, lichens produce a number of unique secondary metabolites through various biosynthetic pathways, namely, acetyl polymalonyl, shikimic acid and mevalonic acid pathways. Most of the lichen substances are phenolic compounds and are reported to have wide variety of biological actions: Antioxidant, antimicrobial, antiviral, anti-inflammatory, analgesic, antipyretic, antiproliferative and cytotoxic effects. Acetyl polymalonyl-derived polyketide compounds, depsides, depsidones, dibenzofuranes, xanthones and naphthaquinones, are of great interest. Compounds from other pathways are esters, terpenes, steroids, terphenylquinones and pulvinic acid. Although manifold biological properties of lichen secondary metabolites have been recognized, their pharmaceutical potential has not been fully explored due to their slow growing nature and difficulties in their artificial cultivation. Many researchers are still working hard to discover and identify the novel lead compounds from lichens. In this chapter, attention has been given to bring in notice some pharmaceutically important lichens and their secondary metabolites and to provide a direction for the study of lichen prospect.