Antioxidant Activities of Three Rubus Species Growing in Ethiopia

In Ethiopian traditional medical practices some species of the genus Rubus (Rosaceae) are used for the treatment of diabetes mellitus, one of the disease conditions in which free radicals and oxidative stress have been implicated. In the present study extracts prepared from three members of the genus, namely Rubus apetalus Poir, R. niveus Thunb and R. steudneri Schweinf were investigated for their in vitro radical scavenging activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and deoxyribose degradation assays. The 80% methanol extract, and acetone and methanol soxhlet fractions of the three plants tested showed antioxidant activity in a concentration-dependent manner. The 80% methanolic extract of R. steudneri showed the strongest activity in the DPPH radical scavenging assay (IC50 = 6.5 mg/ml). In the deoxyribose degradation assay the 80% methanol, acetone and methanol extracts of R. niveus displayed potent activity with IC50 values of 0.64, 0.6 and 0.61 μg/ml, respectively. Ascorbic acid (vitamin C) was used as a positive control in the DPPH assay (IC50 = 4.5 μg/ml) and butylhydroxytoluene, in the deoxyribose degradation assay (IC50 = 4.76 μg/ml). The results of the present study suggest that the antioxidant activity of the studied plants may contribute to their purported uses as antidiabetic agents. The work further indicated that the antioxidant active principles of the plants reside in the polar fraction of the extracts. Keywords: Rubus spp., Rosaceae, radical scavenging activity, DPPH assay, deoxyribose degradation assayEthiopian Pharmaceutical Journal Vol. 25 (2) 2007: pp. 103-11