Isolation, characterization and DFT studies of epoxy ring containing new withanolides from Withania coagulans Dunal

Shahid Ali Khan; Achyut Adhikari; Khurshid Ayub; Aliya Farooq; Saima Mahar; Muhammad Nasimullah Qureshi; Abdur Rauf; Sher Bahadar Khan; Ralf Ludwig; Tariq Mahmood

doi:10.1016/j.saa.2019.03.046

Isolation, characterization and DFT studies of epoxy ring containing new withanolides from Withania coagulans Dunal

Spectrochim Acta A Mol Biomol Spectrosc. 2019 Jun 15:217:113-121. doi: 10.1016/j.saa.2019.03.046. Epub 2019 Mar 19.

Authors

Affiliations

¹ Department of Chemistry, University of Swabi, Swabi 23561, Khyber Pakhtunkhwa, Pakistan; H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, 75270, Pakistan; Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia. Electronic address: shahidsawal007@gmail.com.
² H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, 75270, Pakistan.
³ Department of Chemistry, COMSATS University, Abbottabad Campus, KPK, 22060, Pakistan.
⁴ Department of Chemistry, Shaheed Benazir Bhutto Women University, 31982, Pakistan.
⁵ Department of Chemistry, Sardar Bahadur Khan Woman University Quetta, Pakistan.
⁶ Department of Chemistry, University of Swabi, Swabi 23561, Khyber Pakhtunkhwa, Pakistan.
⁷ Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia.
⁸ Department of Physical Chemistry, University of Rostock, Dr.-Lorenz-Weg 1, 18059 Rostock, Germany; Leibniz-Institut für Katalyse an der Universität Rostock, e. V. Alebert-Einstein-Strasse 29a, 18059 Rostock, Germany.

PMID: 30928836
DOI: 10.1016/j.saa.2019.03.046

Abstract

A new withanolide named as withacoagulin J (1) along with a known withanolide H (2) from Withania coagulans Dunal are reported in this paper. The isolated compounds were elucidated by using 1D-NMR (¹H NMR, ¹³C NMR) and 2D-NMR including homonuclear (COSY, NOESY) and heteronuclear (HSQC, HMBC); along with Mass spectrometry, UV-Visible and IR spectroscopic techniques. The molecular formula based on Fast-Atom Bombardment Mass Spectrometry [FAB-MS (M + 1)] for 1 and 2 were deduced as C₂₈H₃₇O₅ and C₂₈H₃₉O₆ with m/z values 453.2624 and 471.6041, respectively. The quantum mechanical studies of both compounds are based on DFT calculations. The DFT studies show band gaps of 4.86 and 4.83 eV for 1 and 2, respectively. The band gaps of 1 and 2 reflect high stability and resistivity towards oxidation-reduction reactions. The energies of HOMO and LUMO for compound 1 are -6.11 and -1.25 eV and for compound 2: -6.47 and -1.64 eV respectively. Theoretical and experimental FTIR data closely match for both the compounds which support the high accuracy of the computational protocol selection. Other parameters such as bond lengths, bond angles and dihedral angles for both compounds are also studied.

Keywords: Density functional theory; Spectrometry; Spectroscopy; Withania coagulans Dunal; Withanolides.

MeSH terms

Ergosterol / analogs & derivatives
Ergosterol / analysis*
Ergosterol / chemistry
Ergosterol / isolation & purification
Models, Theoretical*
Plant Extracts / chemistry*
Quantum Theory
Withania / chemistry*
Withanolides / analysis*
Withanolides / chemistry
Withanolides / isolation & purification*

Substances

Plant Extracts
Withanolides
Ergosterol