Flavone C-glycosides from Vaccaria pyramidata: Structure elucidation by spectroscopy and theoretical calculations. (February 2019)

• Record Type: Journal Article
• Authors: Said, Ridha Ben; Hamed, Arafa I.; Masullo, Milena; Al-Ayed, Abdullah S.; Moustafa, Mahmoud F.M.; Mahalel, Usama A.; Piacente, Sonia
• Is Part Of: Phytochemistry letters. Volume 29(2019)
• Page Start: 119
• Page End: 124
• Publication Date: 2019-02
• Subjects: Vaccaria pyramidata -- Flavone C-glycosides -- 1D- and 2D NMR experiments -- DFT; Botanical chemistry -- Periodicals; Chimie végétale -- Périodiques; 572.205
• DOI: 10.1016/j.phytol.2018.11.015
• Languages: English
• ISSNs: 1874-3900

Abstract

Graphical abstract: Highlights: The methanol extract of the aerial parts of Vaccaria pyramidata was investigated. Two C-glycoside apigenine derivatives never reported before were characterized by NMR analysis. The structures of the two flavone C-glycosides were confirmed by theoretical study. A known phenolic compound, three triterpenes and a sesquiterpene glycoside were also isolated. Abstract: The flavone C-glycosides namely apigenin-7- O - β -d -glucopyranosyl-8- C - β -d -glucopyranoside (1 ) and apigenin-8- C - α -l -rhamnopyranosyl-(1→2)- O - β -d -glucopyranoside (2 ), along with p -methoxycinnamic acid (3 ), vaccaroside A (4 ), vaccaroside D (5 ), vaccaroside E (6 ) and abscisic acid glucose ester (7 ) were isolated from the methanol extract of the aerial parts of Vaccaria pyramidata. Structure elucidation of compounds1 -7 was accomplished by the extensive use of 1D- and 2D NMR experiments along with HR-ESI-MS. The structures of1 -2 have been confirmed by theoretical study of the 1 H, 13 C chemical shifts and UV data. In addition, Ionization Potential (IP) and Bond Dissociation Enthalpy (BDE) were used to evaluate the theoretical antioxidant activity of compounds1 and2 . TD-DFT method (time-dependent density functional) was used to calculate the electronic absorption spectra of compounds1 and2 from optimized structures in methanol and the orbitals involved in the electronic transition were elucidated.