Tannins and catechin gallate mediate the vasorelaxant effect of Arbutus unedo on the rat isolated aorta.
This study examined the vascular effect of Arbutus leaves (aqueous extract) and described the isolation of several fractions responsible for their vasorelaxant activity. The aqueous extract (AE) of leaves was tested on rat aortic rings precontracted with 0.1 microm noradrenaline. At 10(-2) g/L, AE produced an endothelium dependent relaxation of 66% +/- 5%, (n = 8). The leaves of Arbutus were then extracted successively with different solvents and the methanol extract was the most active. When tannins (primarily condensed tannins) were precipitated from the methanol extract, they showed a strong vasorelaxant activity (87% +/- 4%, n = 5), whereas the elimination of tannins in the methanol extract reduced significantly its vasorelaxant activity (42% +/- 8%, n = 8, p < 0.005). The methanol extract was further separated semi-preparatively by reversed-phase HPLC. Four fractions (Fr2, Fr3, Fr4 and Fr6) were the most active and produced 88% +/- 2% (n = 5), 75% +/- 6% (n = 5), 76% +/- 3% (n = 7) and 77% +/- 3% (n = 10) relaxation, respectively. These four fractions mainly correspond to polyphenol compounds. Analysis of Fr6 indicated that this fraction contained catechin gallate. In conclusion, the vasorelaxant activity of Arbutus is likely to be due to polyphenol compounds, primarily condensed tannins and catechin gallate.
Legssyer
Abdelkhaleq
A
Laboratoire de Physiologie et Pharmacologie Cellulaire, Département de Biologie, Université Mohamed Premier, Faculté des Sciences, BP 524, 60000 Oujda, Morocco. alegssyer@sciences.univ-oujda.ac.ma
Ziyyat
Abderrahim
A
Mekh
Hassane
H
Bnouham
Mohamed
M
Herrenknecht
Christine
C
Roumy
Vincent
V
Fourneau
Christophe
C
Laurens
Alain
A
Hoerter
Jacqueline
J
Fischmeister
Rodolphe
R
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects*; D002392:Catechin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D004730:Endothelium, Vascular / Q000187:drug effects*; D029791:Ericaceae; D008297:Male; D009638:Norepinephrine; D008517:Phytotherapy; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use; D018515:Plant Leaves; D051381:Rats; D017208:Rats, Wistar; D013634:Tannins / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use
D010936:Plant Extracts; D013634:Tannins; D014665:Vasodilator Agents; C417939:catechin gallate; D002392:Catechin; D009638:Norepinephrine