Planta Med 2006; 72 - P_171
DOI: 10.1055/s-2006-949971

Free radical scavenging activity of some Nigerian medicinal plants

MO Sofidiya 1, OA Odukoya 1, OB Familoni 2, SI Inya-Agha 3
  • 1Department of Pharmacognosy, Faculty of Pharmacy
  • 2Department of Chemistry, Faculty of Science, University of Lagos, Nigeria.
  • 3Department of Pharmacognosy, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Nigeria

Antioxidant properties are among the first links between chemical reactions and biological activity. Phenolic natural products are of particular interest because of their antioxidant activity through scavenging oxygen radicals and inhibiting peroxidation. The cure all activity of Nigerian medicinal plant extracts used in traditional medicine practice has been associated with the antioxidant potential of their phenolic content in our laboratory [1].

The present work evaluated the DPPH radical scavenging, total antioxidant activities, reducing power, and total contents of phenolic compounds in methanolic leaf extracts of five Nigerian medicinal plants Dalbergia saxatilis Hook.f. (Papilionaceae), Ekebergia senegalensis A.Juss.(Meliaceae), Hymenocardia acida Tul. (Hymenocardiaceae), Icacina tricantha Oliv.(Icacinaceae) and Salacia pallescens Oliv.(Celastraceae) ]. Free radical scavenging activity was measured spectrophotometrically as maximum fading power of DPPH at 517nm (DPPH is reduced to DPPH-H, with colour change from violet to yellow)at 0.025, 0.05, 0.1, 0.2mg/mL concentration of extracts. Reducing power was determined using Ferricyanide Trichloroacetic acid method and total phenolic content, according to the Folin-Ciocalteu assay.

Antioxidant activity of the plant extracts with the DPPH radical scavenging and reducing power method, were in the order Hymenocardia > Ekebergia > Salacia > Icacina > Dalbergia. H. acida and E. senegalensis possess very high radical scavenging activity in both assays. Potency of H. acida extract (97.4% inhibition) was of the same magnitude as that of reference α – tocopherol. Total phenols in all the samples expressed as GAE (Gallic Acid Equivalent) varied from 1.83 to 15.47mg/g of dry plant material. Free radical scavenging activity correlated with reducing power (R2 =0.9564) and total phenols R2 =0.6640 (y=1.2281 x -103.11) respectively. This suggests that 66% of the antioxidant capacity of these extracts result from contribution of phenolic compounds.

Reference: 1. Odukoya, O.A. et al. (2005), Antioxidant activity of Nigerian Dietary Spices. Electronic J. Environ. Agricult. Food Chem. 4:1086–1093.