Comparative phytochemical analysis of five lichen species [Parmotrema tinctorum (Delise ex Nyl.) Hale, P. andinum (Mull. Arg.) Hale, P. praesorediosum (Nyl.) Hale, P. grayanum (Hue) Hale, P. austrosinense (Zahlbr.) Hale] of Parmotrema genus were performed using two complementary UPLC-MS systems. The first system consists of high resolution UPLC-QToF-MS/MS spectrometer and the second system consisted of UPLC-MS/MS in Multiple Reaction Monitoring (MRM) mode for quantitative analysis of major constituents in the selected lichen species. The individual compounds (47 compounds) were identified using Q-ToF-MS/MS, via comparison of the exact molecular masses from their MS/MS spectra, the comparison of literature data and retention times to those of standard compounds which were isolated from crude extract of abundant lichen, P. tinctorum. The analysis also allowed us to identify unknown peaks/compounds, which were further characterized by their mass fragmentation studies. The quantitative MRM analysis was useful to have a better discrimination of species according to their chemical profile. Moreover, the determination of antioxidant activities (ABTS inhibition) and Advance Glycation Endproducts (AGEs) inhibition carried out for the crude extracts revealed a potential antiglycaemic activity to be confirmed for P. austrosinense.

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Considering the importance of ultra-performance liquid chromatography-electrospray ionization-quadrupole time of flight-tandem mass spectrometry (UPLC-ESI-QTOF-MS/MS) hyphenated techniques for analysis of secondary metabolites from crude extracts, the present study was aimed at identification of secondary metabolites in acetone extract of the lichen Usnea longissima. From our study, 19 compounds were tentatively identified through comparison of exact molecular masses from their MS/MS spectra, mass fragmentation studies and comparison with literature data. In addition, potent cytotoxic activity of U. longissima extract prompted us to isolate four compounds, 18R-hydroxy-dihydroalloprotolichesterinic acid (19), neuropogolic acid (20), barbatic acid (21), and usnic acid (22) from this extract which were adequately identified through mass spectrometry and NMR spectroscopy. All four compounds displayed cytotoxic activity. Barbatic acid (21) manifested doxorubicin equivalent activity against A549 lung cancer cell line with IC50 of 1.78 µM and strong G0/G1 accumulation of cells. Poly ADP-ribose polymerase (PARP) cleavage confirmed that it induced cytotoxic activity via apoptosis. Finally, our work has discerned the depside, barbatic acid (21) from crude extract as a candidate anti-cancer molecule, which induces cell death by stepping up apoptosis.