Investigation of Antimicrobial and Antioxidant Activity ofTephromela atraLichen and its Chemical Isolates, α-Alectoronic Acid and α-Collatolic Acid

Abstract

ABSTRACTLichens and their secondary metabolites are of particular interest as they can be used as an alternative to synthetic drugs in the treatment of various diseases. The present study was carried out to investigate in vitro antioxidant and antimicrobial activities of acetone, dichloromethane, petroleum ether, and methanol extracts of the lichenTephromela atraand its major metabolites. α-alectoronic acid and α-collatolic acid were identified as bioactive substances in the lichenTephromela atra. The antibacterial activity was investigated using the disk diffusion method and the minimum inhibitory concentrations were determined against eleven bacterial species, nine fungal species, and four yeast species using broth microdilution method. The antioxidant activity of the methanol extracts ofTephromela atrawas measured by the free radical scavenging ability using the DPPH method. The extracts of α-alectoronic acid and α-collatolic acid showed significant inhibitory activity against most of the tested bacteria, especially the lowest MIC values of the two acids forBacillus subtilis. Furthermore, the antioxidant activity was determinedin vitroby measuring the radical scavenging capacity of the extracts on DPPH. The methanol extracts showed significant antioxidant activity and high DPPH scavenging activity at all concentrations. The results indicate that the extracts ofTephromela atraand the natural products obtained can be used as a source of antimicrobial and antioxidant agents in the pharmaceutical industry.HIGHLIGHTSThe present study determines the antibacterial and antifungal activities of theTephromela atra, lichen extracts, and its isolated major constituents (α-alectoronic acid and α-collatolic acid), as well as evaluates the antioxidant capacity.Although there are some studies on α-alectoronic acid and α-collatolic acid, isolated in different lichens, there is no study on the biological activity and antioxidant capacity of lichenTephromela atra.The MIC values of isolates were evaluated against a broad range of microorganisms including eleven species of bacteria, nine species of fungi, and four species of yeasts.α-Alectoronic and α-collatolic acid extracts showed significant inhibitory activity against most of the tested bacteria, especially the lowest MIC values of both acids for Bacillus subtilis.Our results provide a future perspective thatTephromela atraextracts and the isolated metabolites might be used as effective antimicrobial and antioxidant agents in pharmaceutical areas.Graphical Abstract