Influence of Extraction Solvent on Antioxidant Properties of Guiera senegalensis J.F. Gmel (Combretaceae) Leaves

Abstract

Guiera senegalensis is widely used in West Africa for traditional medicine. In Northern Nigeria, it is used for general well-being by women during postpartum recovery period. In this study, we report the effect of extraction solvents viz acetone, chloroform, ethanol, methanol (each at 50% and 75% concentrations) and water on the phenolic antioxidant and antioxidant activity of it’s leaves. Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) assays were used to determine the phenolic antioxidants. Antioxidant activity was evaluated by measuring scavenging effect on 2,2ꞌ- diphenyl-1-picrylhydrazyl (DPPH) radical, Ferric Reducing Antioxidant Power (FRAP) and Total Antioxidant Capacity (TAC) using phosphomolybdate assay. Results shows that extraction solvents significantly (P<0.05) affect phenolic antioxidants extraction and antioxidant properties. Highest TPC value (109.20±3.99mg GAE/100g DW) was obtained in 75% ethanol. 75% acetone showed the highest TFC value (414.60±7.60mg QE/100g DW). Highest DPPH radical scavenging activity (95.82±0.63%) was observed in water solvent. 50% chloroform showed the best FRAP value (282.73±29.80mg AAE/100g DW). While 75% methanol showed the highest TAC value (102.44±3.44mg AAE/1g DW). Based on its highest TFC value as well as its insignificant differences with other solvents that showed higher values for TPC, FRAP and TAC, 75% acetone appeared to be the solvent for extracting phenolic antioxidants. Correlations study indicates highly significant positive (p< 0.001) linear correlations between phenolic antioxidants and antioxidant activities. The highest correlation (r² = 0.845) was observed between TFC and TAC followed by TFC and DPPH (r² = 0.733). Another significant correlation (r² = 0.659) was also observed between TFC and FRAP. Further studies aimed at isolating and identifying specific compounds responsible for antioxidant activity in G. senegalensis are recommended.

Keywords: Antioxidant activity, extraction solvents, Guiera senegalensis and phenolic antioxidants