ANTIOXIDANT CAPACITY OF (KLAKLAK)2 BIOCONJUGATES ASSESSED BY THE ELECTRON-TRANSFER METHODS FRAP AND CUPRAC
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2025-11-02
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Abstract
Oxidative stress and metal-driven redox processes are key contributors to the pathogenesis of chronic diseases and cancer, motivating the search for novel antioxidant molecules. In this study, the antioxidant potential of a series of synthetic peptides previously reported to possess antitumor and antibacterial properties was evaluated using two complementary electron-transfer assays: ferric reducing antioxidant power (FRAP) and cupric ion reducing antioxidant capacity (CUPRAC). Both assays were calibrated against caffeic acid, and results were expressed as caffeic acid equivalents (CAE). The FRAP assay revealed substantial differences in reducing activity, with Si8 exhibiting the highest value (0.558 ± 0.132), followed by Si12 (0.478 ± 0.0240), Si10 (0.293 ± 0.0220), and Si15 (0.250 ± 0.0200), whereas Si1 (0.00439 ± 0.00240) and Si11 (0.00260 ± 0.000500) showed negligible responses. A comparable pattern was observed in the CUPRAC assay, where Si8 again displayed the strongest reducing capacity (0.381 ± 0.0948), with Si12 (0.290 ± 0.0225), Si15 (0.262 ± 0.0223), and Si10 (0.224 ± 0.0290) also demonstrating appreciable activity, while Si1 (0.001800 ± 0.000400) and Si11 (0.0132 ± 0.000500) remained inactive. The combined application of FRAP and CUPRAC provided complementary and reproducible measures of peptide antioxidant capacity, establishing a framework for systematic characterization of redox-active peptides in relation to oxidative stress.