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Deniz ürünlerinin toplam antioksidan kapasitesinin spektroskopik tayini

Spectroscopic analysis of total antioxidant capacity of seafood products

  1. Tez No: 893159
  2. Yazar: ELENUR İMERT
  3. Danışmanlar: PROF. DR. BİRSEN ÖZTÜRK, DOÇ. DR. DİLEK ÖZYURT
  4. Tez Türü: Yüksek Lisans
  5. Konular: Kimya, Chemistry
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2024
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Lisansüstü Eğitim Enstitüsü
  11. Ana Bilim Dalı: Kimya Ana Bilim Dalı
  12. Bilim Dalı: Kimya Bilim Dalı
  13. Sayfa Sayısı: 72

Özet

Antioksidanlar, hücrelerde oksidatif strese neden olan serbest radikallerin zararlı etkilerini azaltan veya tamamen engelleyen maddelerdir. Serbest radikaller, hücre metabolizması sırasında doğal olarak oluşan veya çevresel faktörler (örneğin, kirlilik, sigara dumanı, radyasyon) sonucu vücuda giren kararsız moleküllerdir. Bu moleküller, diğer hücre bileşenleriyle (DNA, proteinler, lipitler) reaksiyona girerek hücre hasarına, yaşlanmaya ve çeşitli hastalıklara yol açabilirler. Antioksidanlar, serbest radikallerle reaksiyona girerek veya onların etkisini nötralize ederek serbest radikallerin kimyasal yapılarını kararlı hale getirir. Antioksidan tayini, sağlık, gıda, farmasötik ve çevresel bilimler gibi birçok alanda kritik öneme sahiptir. Bu tayinler, hastalıkların önlenmesi ve tedavisinden, gıda kalitesinin artırılmasına, çevre koruma çalışmalarından kozmetik ürün geliştirilmesine kadar geniş bir yelpazede uygulanır. Bu nedenle, antioksidan kapasitenin doğru ve güvenilir bir şekilde belirlenmesi, hem bilimsel araştırmalar hem de endüstriyel uygulamalar açısından büyük değer taşır. Toplam antioksidan kapasitenin (TAC) doğrudan analiz etme yöntemlerinin geliştirilmesi, günümüzdeki araştırmalarda büyük önem taşımaktadır. TAC, karmaşık bir örnekte bulunan tüm antioksidanların toplam kapasitesini temsil eden bir birleşik parametredir. Bu çalışmanın amacı, antioksidan açısından zengin olduğu bilinen makroalglerin toplam antioksidan kapasitelerinin tayin edilmesi için basit, hızlı, ucuz, ön deriştirme işlemleri gerektirmeden fiber optik reflektans spektrofotometre (FORS) cihazı ve kullanılarak yeni bir yöntem geliştirilmesidir. Bu çalışmanın Fe(III)-FZ kompleksinin antioksidan bileşikleri ile reaksiyona girdiği ideal deney koşullarının belirlenmesi ve belirlenen bu koşullarda bir Fe(III)-FZ yönteminin geliştirilmesidir. İkinci hedef ise gıdaların TAC'lerini belirlemek için spektrofotometrik yöntemlere kıyasla daha hızlı ve daha basit bir yöntem olan reflektometrik yeni bir yöntem geliştirmektir. 562 nm'de maksimum absorbans veren mor/magenta renkli demir(II)-ferrozine (Fe(II)-FZ) kompleksi, genellikle demir bağlama kapasitesinin belirlenmesinde kullanılmasına rağmen, antioksidan tayin yöntemi olarak kullanılmamıştır. Ferrozin, demirin düşük oksidasyon basamağını son derece kararlı hale getirir ve bu özellik, demir(III) iyonlarının ferrozin varlığında antioksidanları kolayca okside etmesine ve kendisinin yüksek molar absorptiviteye sahip Fe(II)-FZ'ye indirgenmesine neden olur. Bu sayede birçok antioksidanın daha hassas bir şekilde tayin edilmesi mümkün hale gelir. Geliştirilen yöntemde antioksidan çözeltileri ile hazırlanan Fe(III)-Ferrozin reaktifi bir reçine üzerine immobilize edilmiş ve renkli Fe(II)-Ferrozin oluşumuyla ilişkili yansıma değişimi 562 nm'de ölçülmüştür. Sonuçlar, CUPRAC (Cu(II) İndirgenme Antioksidan Kapasitesi) ve Fe (III)-FZ yöntemleriyle karşılaştırılmıştır. Yöntem makroalg ekstraktlarına uygulanarak, troloks eşdeğeri cinsinden toplam antioksidan kapasite değeri hesaplanmıştır. Yöntem sonucunda Fe(III)-FZ yöntemi ile antioksidan kapasitesi ölçülemeyen Fisetin, Glutatyon, Morin ve α-tokoferol gibi antioksidanların toplam antioksidan kapasitesinin ölçüldüğü görülmüştür.

Özet (Çeviri)

Oxygenated respiration is the breakdown of food molecules in the presence of oxygen to obtain energy. Humans, animals, bacteria and fungi with high energy needs perform oxygenated respiration. The chemical reaction seen in living organisms that respire with oxygen is called oxidation. Radicals with one or more unpaired electrons formed as a result of oxidation are called free radicals. Antioxidants are substances that reduce or completely neutralize the harmful effects of free radicals, which cause oxidative stress in cells. Free radicals are unstable molecules that are naturally formed during cell metabolism or enter the body as a result of environmental factors (e.g., pollution, cigarette smoke, radiation). These molecules react with other cell components (DNA, proteins, lipids) causing cell damage, aging, and various diseases. Antioxidants react with free radicals or neutralize their effects by stabilizing their chemical structures. The determination of antioxidants is of critical importance in many fields such as health, food, pharmaceutical, and environmental sciences. These determinations are applied in a wide range of areas, from disease prevention and treatment to improving food quality, environmental protection, and the development of cosmetic products. Therefore, the accurate and reliable determination of antioxidant capacity holds significant value both for scientific research and industrial applications. Antioxidant capacity is the amount of substances that protect a cell or body from free radicals. It is possible to use various biochemical and chemical assays to determine total antioxidant capacity. These methods may vary according to the purpose of the analysis and the conditions of the study. Total Antioxidant Capacity indicates the capacity of each antioxidant in a complex sample. It is divided into two groups as hydrogen atom transfer (HAT) and electron transfer (ET) total antioxidant capacity methods. Oxygen Radical Absorbance Capacity Method is based on hydrogen atom transfer and CUPRAC method is based on electron transfer. The ABTS-TEAC method is a method based on both bases. The development of methods for the direct analysis of total antioxidant capacity (TAC) is of great importance in current research. TAC is an integrated parameter that represents the total capacity of all antioxidants present in a complex sample. The Fe(III)-ferrozine method is based on the formation of a complex of Fe(III) with ferrozine and the reduction of this complex to Fe(II)-ferrozine complex by reaction with antioxidants and measurement of the absorbance of the complex at 562 nm. In 2010, Işıl Berker Çetin et al. Iron(III)-ferrozine method was applied to herbal teas. In 2017, Işıl Berker Çetin et al. absorbed samples with low antioxidant value on resin to measure their antioxidant capacity and the method was developed. Algae are the primary producers of aquatic ecosystems and make up 10% of the plant kingdom. They are known as eukaryotic or prokaryotic plant organisms. Microalgae and macroalgae are two types of algae. Macroalgae are ecologically, biologically and economically beneficial. Ecologically, they provide nutrition, reproduction and shelter for other living things, while economically they provide many benefits in human life, such as waste treatment, use as animal feed and fertilizer, and use as food. Macroalgae can be divided into three categories. There are red, green and brown algae. The antioxidant activity of marine macroalgae is a result of pigments such as chlorophyll and ß-carotene, as well as vitamins such as niacin, α-tocopherol and phenol compounds. Fiber optic reflectance spectroscopy involves performing analysis using a spectrophotometer, optical fibers and light. With the help of optical fibers, light is transmitted from the instrument to the target and from the target to the instrument. On-site measurements are possible without the need for sampling. FORS provides useful information for the identification of pigments in works of art and for the analysis of color and its variations in paintings. Fiber optic reflectance spectrophotometers are used to measure light intensity in the visible, near infrared and infrared regions. It is a simple, portable and low-cost device used in many fields, from the causes of discoloration of plastics to the study of tissue biochemistry, from cancer identification to the identification of textile fibers. The instrument consists of a halogen lamp as light source, a micrometer, a reflection probe and a detector. A specially designed sample measuring apparatus was used in the study to ensure that the sample quantity was the same for each measurement. The aim of this study is to develop a new method by combining Fe(III)-Ferrozine method, which is one of the antioxidant capacity determination methods, with Fiber Optic Reflectance Spectroscopy method, which is useful in measuring low antioxidant capacity values as shown by the studies and to apply this method on macroalgae. This method should be simple, fast, and cost-effective. Within the scope of this study, first, the optimal experimental conditions under which the Fe(III)-FZ complex reacts exclusively with antioxidant compounds were determined, and under these conditions, the Fe(III)-Ferrozin method was developed. Secondly, a new reflectometric method was developed as a rapid and simple alternative to spectrophotometric methods for determining the TACs of foods. The magenta-colored iron(II)-ferrozine (Fe(II)-FZ) complex, which shows maximum absorbance at 562 nm, is commonly used to determine iron binding capacity but has not been used as an antioxidant assay method. Ferrozin stabilizes the lower oxidation state of iron so well that iron(III) ions in the presence of ferrozin readily oxidize antioxidants and reduce themselves to Fe(II)-FZ with high molar absorptivity. This allows for a more sensitive determination of many antioxidants. In the developed method, Fe(III)-Ferrozin reagent prepared with antioxidant solutions was immobilized on a resin, and the reflectance change associated with the formation of the colored Fe(II)-Ferrozin was measured at 562 nm. The method was applied to macroalgae extracts, and the total antioxidant capacity value was calculated in terms of trolox equivalents and compared with the results from CUPRAC (Cu(II) Reducing Antioxidant Capacity) and Fe(III)-FZ methods. As a result of the method, it was observed that the total antioxidant capacity of antioxidants such as fisetin, glutathione, morin, and α-tocopherol, which could not be measured with the Fe(III)-FZ method, was determined. In our study, iron(III)ferrozine reagent was attached to a resin and the reflectance change of the colored iron(II)ferrozine complex formed by the reaction with antioxidants was measured at 562 nm. The developed method appears to be simple, rapid and applicable for the determination of antioxidant capacity in standard antioxidant compounds and macroalgae samples. When TEAC coefficients of standard antioxidants were calculated, quercetin was found to have the highest capacity. The antioxidant capacity in macroalgae samples was tested with spectrophotometric Fe(III)-Ferrozine and the accuracy of our method was proven as a result of the close results. In addition, it was observed that some antioxidants whose antioxidant capacity could not be measured by Fe(III)-Ferrozine method could be measured by the method we developed.

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