Development and application of a new antioxidant method with use of a substrate

Pharmaceutical ingredients, food ingredients, and many industrial products are subject to oxidation and, therefore, need antioxidants for stability in normal environments. Thus, there is a need for new methods for the detection of antioxidants that will protect them by using such components as oxidation substrates. For this purpose, in this thesis, a new determination method was developed by studying DPPH radical scavenging, ABTS radical scavenging, and Peroxynitrite scavenging methods and testing various substrates. These three methods and potential substrates have been tested both classically spectrophotometrically, using on-line HPLC-post-column antioxidant activity measurement, and post-reaction HPLC measurement of antioxidant protection. An application method was developed in which antioxidant protection was measured by HPLC after the reaction, and catechin and Trolox were used as model substrates. Optimization and validation studies were carried out on this method, and the developed method was applied to standard antioxidants (Gallic Acid, BHT, Caffeic Acid, and Ascorbic Acid) and Henna extract as a real sample. The new substrate-based DPPH radical protection activity method developed in this thesis study will lead to further studies and this approach has brought the DPPH antiradical activity method to the literature. Keywords: Antioxidant activity, DPPH, Henna, HPLC, Substrate