Planta Med 2015; 81 - PM_57
DOI: 10.1055/s-0035-1565434

Antioxidant activity of the root extract of Combretum dolichopetalum and the isolated constituents

PF Uzor 1, PO Osadebe 1, Z Liu 2, W Ebrahim 2, 3, P Proksch 2
  • 1Department of Pharmaceutical and Medicinal Chemistry, University of Nigeria, Nsukka, 410001, Nigeria
  • 2Heinrich-Heine-Universität, Institut für Pharmazeutische Biologie und Biotechnologie, Universitatsstrasse 1, Geb. 26.23, Düsseldorf, 40225, Germany
  • 3Department of Pharmacognosy, Faculty of Pharmacy, Mansoura University, Mansoura 35516, Egypt

Natural antioxidants from plants such as ascorbic acid, tocopherol, carotenes, phenolic acids and phytoestrogens have been recognized as having the potential to reduce the risk for diabetes and other chronic diseases. Combretum dolichopetalum Engl. and Diels (Combretaceae) aqueous root extract is used traditionally in management of diabetes and in stomach disorders. The aim of the present research is to investigate the antioxidant activities of C. dolichopetalum root extract and to isolate the antioxidant constituents.

On successive solvent-solvent partitioning, the methanol extract (ME) of C. dolichopetalum root afforded the ethyl acetate (EAF) and butanol (BuF) fractions. Through various chromatographic separations, arjunolic acid (1) and dihydrophaseic acid (2) were isolated from EAF, while ellagic acid (3) and 3,4,3'-tri-O-methylellagic acid (4) were obtained from BuF. The compounds were identified based on their 1H- and 13C-NMR, mass spectra and comparison of the data with literature reports. The in vitro antioxidant activity of the extract, fractions and isolated compounds was assessed using the 2,2- diphenyl-1-picrylhydrazinyl (DPPH) and compared to the standard drug ascorbic acid.

Results showed that the ME, EAF, BuF and compound 3 possessed antioxidant activity (IC50= 540.00 ± 6.34, 538.02 ± 2.78, 165.43 ± 10.10, 30.00 ± 1.25 µg/mL respectively) which were lower than that of ascorbic acid (IC50= 16.20 ± 0.69 µg/mL). Compounds 1, 2 and 4 showed no inhibition of DPPH.

It is concluded that C. dolichopetalum root possesses antioxidant activity and ellagic acid is identified as the main antioxidant principle of the plant.