Effects of Tannin Extract fromGongronema latifoliumLeaves on LipoxygenaseCucumeropsis maniiSeeds
Lipoxygenase (EC 1.13.11.12) was partially purified from germinated seeds ofCucumeropsis maniito a purification fold of 47.14, enzyme activity recovery of 72.18%, and specific activity of 326.25 units/mg protein, using a three-step process of centrifugation, ammonium sulphate precipitation and gel filtration. Kinetic properties show maximum activity at pH 6.0 and at optimum temperature of 40°C. Inhibitory effects of the extract fromGongronema latifoliumand two other known antioxidants: ascorbic acid and propyl gallate on lipoxygenase fromCucumeropsis maniiwere studied. Result shows presence of inhibition with IC50 of4.2×10−3±0.09×10−3 g/L,4.3×10−2±0.11×10−2 g/L and7.9×10−2±0.11×10−2 g/L for the extract from ascorbic acid and propyl gallate, respectively. The extract when compared to the other antioxidants exhibits a competitive mechanism of inhibition. This tannin extract could be included during food processing as preservative against food deterioration that might be caused by oxidative enzymes such as lipoxygenase.