Chemical composition of Hypogymnia physodes lichen and biological activities of some its major metabolites

The aim of this study is to investigate chemical composition of acetone extract of the lichen Hypogymnia physodes and antioxidant, -microbial, and -cancer activities of some its major metabolites. Four depsidones (fumarprotocetraric-, 3-hydroxyphysodalic-, physodalic-, and physodic acids), two depsides (atranorin and chloroatranorin), and usnic acid were identified from the lichen H. physodes growing in Serbia using high-performance liquid chromatography with photodiode array detector. Antioxidant activity of isolated metabolites was evaluated by free radical scavenging, superoxide anion radical scavenging, and reducing power. As a result of this study physodic acid was found to have stronger antioxidant activities. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method. All isolated compounds were highly active with minimum inhibitory concentration values ranging from 0.0008 to 1 mg/ml. Anticancer activity was tested against FemX (human melanoma) and LS 174 (human colon carcinoma) cell lines using microculture tetrazolium method. Tested compounds were found have strong anticancer activity toward both cell lines with IC₅₀ values ranging from 12.72 ± 0.35 to 24.63 ± 2.15 μg/ml. The present study shows that isolated lichen compounds demonstrated strong antioxidant, -microbial, and -cancer effects. The results suggest that this lichen can be used as new sources of the natural antimicrobial agents, antioxidants, and -cancer compounds.