Antioxidant activity and phenolic content in three lupin species

Total phenolic compounds, phenolic acids and flavonoid contents and antioxidant activities were measured in extracts from seeds of Lupinus albus, Lupinus luteus and Lupinus angustifolius cultivars. The total phenolic compound contents varied from 491.51 to 731.14 mg/100 g d.m. for cvs. Butan (L. albus) and Parys (L. luteus), respectively. Protocatechuic acid was the most abundant in seeds of yellow lupin (up to 73.60 mg/kg d.m.), whereas p-hydroxybenzoic acid in narrow-leaf lupin (about 43 mg/kg d.m.). The HPLC (high performance liquid chromatography) analysis revealed two dominant flavonoid compounds, which were identified by HPLC/MSⁿ to be apigenin-6,8-di-C-β-glucopyranoside and apigenin 7-O-β-apiofuranosyl-6,8-di-C-β-glucopyranoside. The highest content of the apigenin glycosides was recorded in yellow lupin while the lowest in white lupin. A positive correlation between the content of the analyzed compounds and the antioxidant activity measured by 2,2′-diphenyl-1-picrylhydrazyl (DPPH) method was established, but no such relation was found using the radical-trapping antioxidant parameter (TRAP) method. Modification of the peroxyl radical-trapping potential of lupin extracts by formation of phenoxyl radicals is suggested.