Abstract
A phytochemical study of the flowers of Citharexylum spinosum L. affords the isolation of a new iridoid glycoside, spinomannoside, together with seven known compounds. The isolates were evaluated for their cytotoxic, anti-tyrosinase and anti-cholinesterase activities. Molecular docking and SAR analysis has been sufficiently and widely discussed.
•Phytochemical and biological studies of Citharexylum spinosum L. tree were carried out.•A series of iridoid glycosides were isolated and identified by spectroscopic means.•Isolated compounds were evaluated for their anti-tyrosinase, anticholinesterase and cytotoxic activities.•Caudatoside E, the significant bioactive compound, was docked to the crystal structures of the related proteins.
For several years, chemicals with plant sources are of significant interest mainly for its amazing therapeutic properties and particularly at the structural level. For this reason, a phytochemical investigation and a biological evaluation were performed on the Tunisian Citharexylum spinosum L. tree. The n-butanol extract of flowers from this plant was fractionated by silica gel column chromatography and its fractions have been purified using preparative HPLC, which led to the isolation of a new iridoid glycoside named spinomannoside, as well as seven other known identified as 5-deoxypulchelloside I, pulchelloside I, lamiide, durantoside I, lamiidoside, and caudatosides B and E. The structures of the isolates were established by spectroscopic means including 1D and 2D NMR experiments, and spectrometric ESI-HRMS analysis. Furthermore, the isolated compounds were evaluated in vitro for their anti-tyrosinase, anticholinesterase, and cytotoxic activities. Caudatoside E displayed the highest anti-tyrosinase effect, with a percent of inhibition value of 69.3 ± 2.8 %. Also, the highest anticholinesterase effect was given by caudatoside E with an IC50 value of 22.38 ± 1.82 μM. Lamiidoside and caudatoside E were found to be the most cytotoxic compounds against the human cervical cancer cell line (HeLa) with IC50 values of 17.28 ± 1.40 and 19.02 ± 0.90 μM, respectively. The study of the structure-activity relationship (SAR) has been sufficiently discussed. Caudatoside E, the most active compound, was docked with the protein crystal structures of the PDBs: 2Y9X, 4B0P, and 4I5I.