Abstract:
Convolvulus trabutianus Schweinf. & Muschl is an endemic plant from northern Sahara used in
folk medicine. The purpose of this work is the phytochemical and pharmacological investigation
that led to the isolation of the molecules responsible for the radical scavenging capacity of this
species. The CHCl3, AcOEt and n-BuOH soluble parts of the hydro-ethanol extract (8:2) of the
aerial parts were evaluated for their free radical scavenging capacity by on-line (HPLC-ABTS•+)
assay. The obtained data were confirmed off line by TEAC and ORAC assays.
A subsequent fractionations by HPLC reverse phase followed by spectroscopic analysis (HRMS,
UV, NMR: 1H, 13C, COSY, HSQC and HMBC) were applied to identify the structure of the active
compounds. Twenty three compounds of different categories were identified, among which nine
phenolic acids: ferulic acid ethyl ester 2, p-coumaric acid ethyl ester 6, caffeic acid ethyl ester 10,
vanillic acid 11, ferulic acid 12, alfrutamide 13, 4-hydroxy -benzoic acid 14, p-coumaric acid 15,
caffeic acid 16, two phytosterols: stigmasterol 3 and beta-sitosterol 4 as a mixture (73% and
27%, respectively), four coumarins: 7-O-prenylscopoletin 5, isoscopoletin 7, scoparone 8 and
scopoletin 9, two quinic acids: 3,5-di-caffeoylquinic acid 21 and 4,5-di-caffeoylquinic acid 22
and six flavonoids: chrysoeriol 1, astragalin 17, vicenin-2 18, isoscutellarein 6-C-β-Dglucopyranosyl 19, nicotiflorin 20 and vitexin 23.
All the extracts showed a significant antioxidant activity on-line. The most active compounds
were caffeic acid ethyl ester 10, caffeic acid 16, 3,5-di-caffeoylquinic acid 21 and 4,5-dicaffeoylquinic acid 22. These results were validated off-line by ORAC and TEAC assays. Four
compounds: 1, 5, 18 and 19 were described for the first time from the Convolvulaceae family,
whereas compounds 2, 6, 8, 10, 13 and 21 were new for the genus Convolvulus.
These results show a rich chemical composition and varied in secondary metabolites more
precisely the phenolic compounds which have exhibited a very high antioxidant activity.
