Phytochemical study of the trunk bark of Citharexylum spinosum L. growing in Tunisia: Isolation and structure elucidation of iridoid glycosides

Abstract

A phytochemical investigation of the trunk bark ethyl acetate extract of Citharexylum spinosum L. has led to the isolation of four previously undescribed iridoid glycosides, tunispinosides A-D, and five known phenylethanoid glycosides, verbascoside, leucosceptoside A, martynoside, isoverbascoside and plantainoside C, together with 4-hydroxy-2,6-dimethoxyphenyl 6'-O-vanilloyl-β-D-glucopyranoside, two 8,3'-neolignan glycosides, plucheosides D₁-D₂, coniferyl aldehyde, vanillic acid, syringic acid, ferulic acid and tyrosol. All compounds were isolated for the first time from C. spinosum. Their isolation was carried out using silica gel column and high performance liquid chromatography (HPLC). Structures were established by spectroscopic means including 1D and 2D NMR experiments, and spectrometric ESI-HRMS analysis.

Keywords: 8,3′-neolignan glycosides; Citharexylum spinosum L.; ESI-HRMS; HPLC; Iridoid glycosides; NMR; Phenylethanoid glycosides; Phytochemical investigation; Tunispinosides A-D; Verbenaceae.