Journal of Medicinal Plant Research Vol. 1 (4), 066- 079, November 2007          
ISSN 1996-0875 © 2007 Academic Journals

Full Length Research Paper

Cell protective antioxidants from the root bark of Lannea velutina A. Rich., a Malian medicinal plant

Ababacar Maiga^1,2, Karl Egil Malterud¹, Gro H. Mathisen³, Ragnhild E. Paulsen³, Jane Thomas-Oates⁴, Ed Bergström⁴, Leon Reubsaet⁵, Drissa Diallo² and Berit Smestad Paulsen^1*

¹Section Pharmacognosy, Department of Pharmaceutical Chemistry, School of Pharmacy, University of Oslo, Norway

²Department of Traditional Medicine, Bamako, Mali.

³Department of Pharmaceutical Bioscience, School of Pharmacy, University of Oslo, Norway.

⁴Department of Chemistry, University of York, Heslington, United Kingdom.

⁵Section Pharmaceutical Analysis, Department of Pharmaceutical Chemistry, School of Pharmacy, University of Oslo, Norway.

*Corresponding author. E-mail: b.s.paulsen@farmasi.uio.no  Phone: +4722856572. Fax: +4722854402

Accepted 20 September, 2007

Antioxidants (radical scavengers and 15-lipoxygenase inhibitors) in semipolar extracts of root bark from the Malian medicinal plant Lannea velutina have been investigated. A series of proanthocyanidins with degree of polymerization from 2 to more than 12 have been isolated, in addition to the monomeric substance, catechin. The major constituents have a degree of polymerization of ten or more. Most structures are proposed to be derived from a common biosynthetic route in which catechin is introduced as the terminal unit and epicatechin units are extenders. Catechin, dimeric, trimeric, decameric and dodecameric proanthocyanidins have been assayed as scavengers of the stable free radical diphenylpicrylhydrazyl and as inhibitors of the peroxidizing enzyme 15-lipoxygenase. All of them were shown to be effective radical scavengers (50% radical scavenging at concentrations of 5-7 microgram/mL) and 15-lipoxygenase inhibitors (50% inhibition at 10 - 18 microgram/mL). When epicatechin and trimeric proanthocyanidin were tested as antioxidants in cells, they gave a significant reduction in endogenously produced reactive oxygen species (ROS).

Key words: Lannea velutina, Anacardiaceae, medicinal plant, antioxidant, radical scavenging, 15-lipoxygenase, proanthocyanidins, electrospray mass spectrometry.