Abstract
Methanolic extracts obtained by manual solvent extraction (MSE) and accelerated solvent extraction (ASE) of different Sudanese plant materials (Sclerocarya birrea leaves, Salvadora persica bark and leaves, Combretum hartmannianum leaves, Guiera senegalensis leaves and roots) were investigated for their antioxidant activity. There was no significant difference between the two extraction methods (p < 0.01) regarding the total amount of phenolic compounds expressed as gallic acid equivalents (GAE) (52.6-166.7 mg GAE/g total extractable compounds for MSE and 53.1-169.3 mg GAE/g for ASE). In comparison to a control without extract, the extracts were remarkably effective in the beta-carotene bleaching method, whereas the effectiveness was half or less in comparison to Trolox as standard antioxidant. Also using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) method antioxidant activity could be shown in comparison to a control, however, the extracts were less effective than Trolox. No significant difference was found between the two extraction methods. The increase of the peroxide value of sunflower oil during storage at 70 degrees C was markedly lower after addition of the extracts in comparison to the control, but in the Rancimat test (120 degrees C) the extracts showed only a small stabilization factor (F = 0.9-1.4) especially in comparison to Trolox (F = 5.8).