Comprehensive Analysis of Secondary Metabolites in <i>Usnea longissima</i> (Lichenized Ascomycetes, Parmeliaceae) Using UPLC-ESI-QTOF-MS/MS and Pro-Apoptotic Activity of Barbatic Acid
S. Divya Reddy,
Bandi Siva,
Katragunta Kumar,
V. S. Phani Babu,
Vemireddy Sravanthi,
Joel Boustie,
V. Lakshma Nayak,
Ashok K Tiwari,
CH. V. Rao,
B. Sridhar,
P. Shashikala,
K. Suresh Babu
Affiliations
S. Divya Reddy
Centre for Natural Products & Traditional Knowledge, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Telangana, India
Bandi Siva
Centre for Natural Products & Traditional Knowledge, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Telangana, India
Katragunta Kumar
Centre for Natural Products & Traditional Knowledge, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Telangana, India
V. S. Phani Babu
Centre for NMR & Structural Chemistry, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, Telangana, India
Vemireddy Sravanthi
Organic Synthesis and Process Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, Telangana, India
Joel Boustie
Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes)—UMR 6226, F-35000 Rennes, France
V. Lakshma Nayak
Division of Applied Biology, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Telangana, India
Ashok K Tiwari
Centre for Natural Products & Traditional Knowledge, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Telangana, India
CH. V. Rao
Pharmacognosy and Ethnopharmacology Division, CSIR-National Botanical Research Institute Rana Pratap Marg, P.O. Box No. 436, Lucknow 226001, Uttar Pradesh, India
B. Sridhar
Analytical Division, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Telangana, India
P. Shashikala
Dept. of Pharmacy, University College of Technology, Osmania University, Hyderabad 500 007, Telangana, India
K. Suresh Babu
Centre for Natural Products & Traditional Knowledge, CSIR-Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 007, Telangana, India
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.
