Find in Library

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 <i>Usnea longissima</i>. 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 <i>U. longissima</i> extract prompted us to isolate four compounds, 18<i>R</i>-hydroxy-dihydroalloprotolichesterinic acid (<b>19</b>), neuropogolic acid (<b>20</b>), barbatic acid (<b>21</b>)<b>,</b> and usnic acid (<b>22</b>) from this extract which were adequately identified through mass spectrometry and NMR spectroscopy. All four compounds displayed cytotoxic activity. Barbatic acid (<b>21</b>) manifested doxorubicin equivalent activity against A549 lung cancer cell line with IC₅₀ of 1.78 &#181;M 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 (<b>21</b>) from crude extract as a candidate anti-cancer molecule, which induces cell death by stepping up apoptosis.