Olivetoric acid

Pseudevernia furfuracea (L.) Zopf (Parmeliaceae) is a well-known epiphytic lichen commonly used in Indian spice mixtures and food preparations such as curries. This study is an attempt to find the best extraction methodology with respect to extractive yield, total polyphenolic content (TPC), total flavonoid content and antioxidant activities of lichen P. furfuracea. Two phenolic compounds, atraric acid and olivetoric acid were isolated and quantified in their respective extracts with the aid of reverse phase high performance liquid chromatography (RP-HPLC). The highest concentration of both the compounds, atraric acid (4.89 mg/g DW) and olivetoric acid (11.46 mg/g DW) were found in 70% methanol extract. A direct correlation was also observed between the concentrations of these compounds with the free radical scavenging potential of the extracts which might contribute towards the antioxidant potential of the extract. Moreover, scanning electron microscopy and HPLC analysis which was used to study the effect of pre-processing on extraction process highlighted the capacity of a mixer grinder technique for improved separation of surface localized metabolites and enrichment of the fraction. An investigation of the chemical profile of the bioactive extract 70% methanol extract using UHPLC-DAD-MS lead to tentative identification of forty nine compounds. This extract was also assessed towards HEK 293 T cell line for cytotoxicity analysis. Concentration range of 0.156 to 100 µg/ml of PF70M extract exhibited no significant cell death as compared to control. Further, the active extract showed protective effect against hydroxyl radical's destructive effects on DNA when assessed using DNA nicking assay. Based upon this, it can be concluded that optimization of extraction solvent, sample pre-proceesing and extraction techniques can be useful in extraction of specific antioxidant metabolites.

Primary biosynthetic enzymes involved in the synthesis of lichen polyphenolic compounds depsides and depsidones are non-reducing polyketide synthases (NR-PKSs), and cytochrome P450s. However, for most depsides and depsidones the corresponding PKSs are unknown. Additionally, in non-lichenized fungi specific fatty acid synthases (FASs) provide starters to the PKSs. Yet, the presence of such FASs in lichenized fungi remains to be investigated. Here we implement comparative genomics and metatranscriptomics to identify the most likely PKS and FASs for olivetoric acid and physodic acid biosynthesis, the primary depside and depsidone defining the two chemotypes of the lichen Pseudevernia furfuracea. We propose that the gene cluster PF33-1_006185, found in both chemotypes, is the most likely candidate for the olivetoric acid and physodic acid biosynthesis. This is the first study to identify the gene cluster and the FAS likely responsible for olivetoric acid and physodic acid biosynthesis in a lichenized fungus. Our findings suggest that gene regulation and other epigenetic factors determine whether the mycobiont produces the depside or the depsidone, providing the first direct indication that chemotype diversity in lichens can arise through regulatory and not only through genetic diversity. Combining these results and existing literature, we propose a detailed scheme for depside/depsidone synthesis.

Lichens are symbiotic organisms which are composed fungi and algae and/or cyanobacteria. They produce a variety of characteristic secondary metabolites. Such substances have various biological properties including antimicrobial, antiviral, and antitumor activities. Angiogenesis, the growth of new vessels from pre-existing vessels, contributes to numerous diseases including cancer, arthritis, atherosclerosis, infectious, and immune disorders. Antiangiogenic therapy is a promising approach for the treatment of such diseases by inhibiting the new vessel formation. Technological advances have led to the development of various antiangiogenic agents and have made possible antiangiogenic therapy in many diseases associated with angiogenesis. Some lichens and their metabolites are used in the drug industry, but many have not yet been tested for their antiangiogenic effects. The cytotoxic and angiogenic capacities of lichen-derived small molecules have been demonstrated in vivo and in vitro experiments. Therefore, some of them may be used as antiangiogenic agents in the future. The secondary compounds of lichen whose antiangiogenic effect has been studied in the literature are usnic acid, barbatolic acid, vulpinic acid, olivetoric acid, emodin, secalonic acid D, and parietin. In this article, we review the antiangiogenic effects and cellular targets of these lichen-derived metabolites.