Fast characterization of C-glycoside acetophenones in Medemia argun male racemes (an Ancient Egyptian palm) using LC-MS analyses and computational study with their antioxidant effect

Abstract

Medemia argun is an ancient endemic palm growing in Nubian Desert of Egypt and Sudan. Liquid chromatography coupled with mass spectrometry in negative ion mode (LC/ESI-MS) has proved to be a potent tool for rapid identification and characterization of complex phytochemicals in male racemes of M. argun. A total of seven compounds were tentatively identified comprising of two C-glycoside acetophenones, along with the known compounds one stilbene derivative and four known flavonol derivatives from 40% methanolic portion. The product ions of acetophenone derivatives [M−H]– were shown to be cross-ring cleavages of the hexoside moiety [M-(90/120)-H]– characteristic for C-glycoside linkage. The position of CC-linkage was elucidated by DFT study using the Fukui functions and descriptors. The results revealed that hexose was conjugated with aglycones at C3 or C5. In addition, the theoretical antioxidant activity of compounds 6 and 7 was evaluated by using Bond Dissociation Enthalpy (BDE).