Browsing by Author "Stoyanova Y."

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    ANTIOXIDANT CAPACITY OF (KLAKLAK)2 BIOCONJUGATES ASSESSED BY THE ELECTRON-TRANSFER METHODS FRAP AND CUPRAC
    (2025-11-02) Stoyanova Y.; Jaber S.; Naydenova E.; Georgieva N.; Danalev D.
    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.
  • No Thumbnail Available
    Item
    RADICAL-SCAVENGING ACTIVITY OF (KLAKLAK)2 BIOCONJUGATES WITH CAFFEIC ACID
    (2025-11-02) Stoyanova Y.; Jaber S.; Dinev Y.; Naydenova E.; Georgieva N.; Danalev D.
    Free oxygen radicals released in the body because of various metabolic processes could lead to the so-called oxidative stress in cells, which is a precursor to various types of cancer. Protecting cells from oxidative stress is an important step in the prevention of cancer. Nature has a large supply of compounds with powerful antioxidant properties. One of them is caffeic acid. In the present study, caffeic acid was combined to obtain bioconjugates with analogues of the natural peptide with proven antitumor properties (KLAKLAK)2. Here we report the antioxidant potential of these molecules as it was investigated with the well-known from the literature DPPH method, in search of a synergistic effect between the two pharmacophores of the molecule. The obtained results identify Si18 (Caf-(KnLAKnLAK)2-NH2) as the lead candidate approaching the caffeic acid benchmark under the tested conditions with EC50 = 0.0178 mM.