Biological Activities of Toninia candida and Usnea barbata Together with Their Norstictic Acid and Usnic Acid Constituents

Branislav Ranković,Nedeljko Manojlović,Marijana Kosanić,Tatjana Stanojković,Perica Vasiljević

doi:10.3390/ijms131114707

Branislav Ranković, Nedeljko Manojlović + Show 3 more

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https://doi.org/10.3390/ijms131114707

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Abstract

The aim of this study was to investigate the chemical composition of acetone extracts of the lichens Toninia candida and Usnea barbata and in vitro antioxidant, antimicrobial, and anticancer activities of these extracts together with some of their major metabolites. The chemical composition of T. candida and U. barbata extracts was determined using HPLC-UV analysis. The major phenolic compounds in these extracts were norstictic acid (T. candida) and usnic acid (U. barbata). Antioxidant activity was evaluated by free radical scavenging, superoxide anion radical scavenging, reducing power and determination of total phenolic compounds. Results of the study proved that norstictic acid had the largest antioxidant activity. The total content of phenols in the extracts was determined as the pyrocatechol equivalent. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration using the broth microdilution method. The most active was usnic acid with minimum inhibitory concentration values ranging from 0.0008 to 0.5 mg/mL. Anticancer activity was tested against FemX (human melanoma) and LS174 (human colon carcinoma) cell lines using the microculture tetrazolium test. Usnic acid was found to have the strongest anticancer activity towards both cell lines with IC50 values of 12.72 and 15.66 μg/mL.

Highlights

Lichens are symbiotic organisms built from fungi and a photosynthetic partner, which is either alga or Cyanobacterium [1,2,3]
This paper deals with the phytochemical analysis of acetone extracts from the species T. candida and U. barbata, lichens growing in Serbia, and the isolation of their major metabolites
In addition to the main chemical compound, stictic acid, protocetraric acid, usnic acid and atranorin were identified in the acetone extract of T. candida

Summary

Introduction

Lichens are symbiotic organisms built from fungi and a photosynthetic partner, which is either alga or Cyanobacterium [1,2,3] They usually grow on rocks, non-fertile ground, and as epiphytes on trees and leaves [4]. Mostly by a fungal metabolism, various bioactive secondary components, that sometimes constitute even more than 30% of the dry mass of talus [7] They are found as crystal deposits on the surface of hiphes. More than one hundred secondary metabolites, mainly monoaromatics, depsides, depsidones, pulvinates, dibenzofurans, anthraquinones and xanthones, characteristic of lichens have been detected and isolated [9]. Chemicals structures of these classes of compounds are similar and identification is often very difficult

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