Chemical composition and bioactive properties of the lichen, Pleurosticta acetabulum

Purpose: To investigate the chemical composition and bioactivity of the acetone extract of Pleurosticta acetabulum lichen. Methods: Phytochemical analysis of the acetone extract of the lichen (Pleurosticta acetabulum) was carried out by high-performance liquid chromatography (HPLC). The antioxidant activity of the lichen extract was evaluated by determining the radical scavenging capacity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and reducing power. To determine total phenolics and flavonoids, we used spectrophotometric methods. Antimicrobial activity was estimated by determination of the minimal inhibitory concentration using broth microdilution method. Anticancer activity of the lichen extract was tested using 3-4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT). Results: Salazinic, norstictic, protocetraric, evernic acid and atranorin were identified as compounds of lichen. P. acetabulum extract exhibited moderate free radical scavenging activity (half-maximum inhibitory concentration, IC50 of 151.7301 µg/mL). The spectrophotomeric absorbance of the extract for reducing power varied from 0.035 to 0.127, while the total phenolics and flavonoids in the extract were 35.39 µg PE/mg and 12.74 μg RE/mg, respectively. Minimum inhibitory concentration (MIC) was in the range of 1.25 to 20 mg/mL while cytotoxic activity (based on IC50 values) ranged from 24.09 to 45.94 µg/mL. Conclusion: The results confirm that lichen extract contains secondary metabolites that possess antioxidant, antimicrobial and anticancer activities, which opens up some possibilities for the extract to be developed as food supplements and pharmaceutical raw materials. Keywords: Pleurosticta acetabulum, Antioxidant activity, Antimicrobial activity, Cytotoxic activity, Liche