Antioxidant activity of brown lead (Leucaena leucocephala) seed extracts with and without prior chlorophyll removal was studied in comparison with mimosine. Both extracts showed similar hydroxyl radical (HO(•)) scavenging activity, hydrogen peroxide (H2O2) scavenging activity, singlet oxygen inhibition and hypochlorous acid (HOCl) scavenging capacity (p > 0.05). Nevertheless, the extract without prior chlorophyll removal had higher oxygen radical absorbance capacity than that with prior chlorophyll removal (p < 0.05). Generally, lead seed extracts with and without prior chlorophyll removal possessed a lower antioxidant activity, compared with mimosine. When lead seed extract without prior chlorophyll removal (100 and 200 ppm) was used in different lipid oxidation model systems, including β-carotene-linoleic acid and lecithin liposome systems, the preventive effect toward lipid oxidation was dose-dependent. At the same level of use, mimosine exhibited a higher efficacy in prevention of lipid oxidation in both systems as indicated by the lower increases in thiobarbituric acid reactive substances. A similar result was obtained in minced mackerel. Therefore, lead seed extract containing mimosine could act as a natural antioxidant to prevent lipid oxidation in foods.
Keywords: Lead seed extract; antioxidant; food model system; lipid oxidation; mimosine; radical scavenging activity.