Ahmet C. Gören

Bio: Ahmet C. Gören is an academic researcher from Bezmialem Foundation University. The author has contributed to research in topics: Essential oil & DPPH. The author has an hindex of 31, co-authored 156 publications receiving 3566 citations. Previous affiliations of Ahmet C. Gören include Istanbul Technical University & Ağrı İbrahim Çeçen University.

Antioxidant activity and phenolic compounds of ginger (Zingiber officinale Rosc.) determined by HPLC-MS/MS

Abstract: Oxidative stress related diseases often arise from over production of free radicals and reactive oxygen/nitrogen species. The prevention of these diseases could be possible with the use of natural antioxidant plants that could be promising as therapeutic candidates. Since antioxidant properties of a species could be stem from phenolic compounds, it is, therefore, important to evaluate antioxidant and total/individual phenolic and flavonoid content. For this purpose, we evaluated antioxidant properties of ginger (Zingiber officinale Rosc.) based on three parameters: the antioxidant capacity, total phenolic and flavonoid content as well as identification of phenolic acids of water extract (WEG) and ethanol extract (EEG) of ginger. For antioxidant capacity, we performed FRAP, CUPRAC assay, Fe2+ chelating ability, DPPH and DMPD radical scavenging activities. Also, total phenolic and flavonoid contents in both extracts were also measured via Folin Ciocalteu’s method. For identification of phenolic acids, HPLC-MS/MS method was performed. The results showed that EEG had generally better antioxidant activity than WEG in all assays. HPLC-MS/MS analysis showed that there are at least eight different phenolic acids found in ginger, among which pyrogallol p-hydroxybenzoic acid, ferulic acid and p-coumaric acid were more abundant in both extracts. This study clearly showed that ginger extracts demonstrated effective antioxidant properties and their consumption may reduce or delay the progression of diseases that oxidative stress take place due to lack of antioxidant supplementation.

Pomological features, nutritional quality, polyphenol content analysis, and antioxidant properties of domesticated and 3 wild ecotype forms of raspberries (Rubus idaeus L.).

Abstract: The raspberry (Rubus idaeus L.) is an economically important berry crop that contains many phenolic compounds with potential health benefits. In this study, important pomological features, including nutrient content and antioxidant properties, of a domesticated and 3 wild (Yayla, Yavuzlar, and Yedigol) raspberry fruits were evaluated. Also, the amount of total phenolics and flavonoids in lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were calculated as gallic acid equivalents (GAEs) and quercetin equivalents (QE). The highest phenolic compounds were found in wild Yayla ecotype (26.66 ± 3.26 GAE/mg extract). Whilst, the highest flavonoids were determined in wild Yedigol ecotype (6.09 ± 1.21 QA/mg extract). The antioxidant activity of lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were investigated as trolox equivalents using different in vitro assays including DPPH(•), ABTS(•+), DMPD(•+), and O(•-)(2) radical scavenging activities, H(2)O(2) scavenging activity, ferric (Fe(3+)) and cupric ions (Cu(2+)) reducing abilities, ferrous ions (Fe(2+)) chelating activity. In addition, quantitative amounts of caffeic acid, ferulic acid, syringic acid, ellagic acid, quercetin, α-tocopherol, pyrogallol, p-hydroxybenzoic acid, vanillin, p-coumaric acid, gallic acid, and ascorbic acid in lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were detected by high-performance liquid chromatography and tandem mass spectrometry (LC-MS-MS). The results clearly show that p-coumaric acid is the main phenolic acid responsible for the antioxidant and radical scavenging activity of lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits.

Antioxidant activity of food constituents: an overview

Abstract: Recently, there has been growing interest in research into the role of plant-derived antioxidants in food and human health. The beneficial influence of many foodstuffs and beverages including fruits, vegetables, tea, coffee, and cacao on human health has been recently recognized to originate from their antioxidant activity. For this purpose, the most commonly methods used in vitro determination of antioxidant capacity of food constituents are reviewed and presented. Also, the general chemistry underlying the assays in the present paper was clarified. Hence, this overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. In addition, the most important advantages and shortcomings of each method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS·+) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging, Fe3+–Fe2+ transformation assay, ferric reducing antioxidant power (FRAP) assay, cupric ions (Cu2+) reducing power assay (Cuprac), Folin-Ciocalteu reducing capacity (FCR assay), peroxyl radical scavenging, superoxide anion radical (O 2 ·− ) scavenging, hydrogen peroxide (H2O2) scavenging, hydroxyl radical (OH·) scavenging, singlet oxygen (1O2) quenching assay and nitric oxide radical (NO·) scavenging assay are outlined and critically discussed. Also, the general antioxidant aspects of main food components were discussed by a number of methods which are currently used for detection of antioxidant properties food components. This review consists of two main sections. The first section is devoted to main components in the foodstuffs and beverages. The second general section is some definitions of the main antioxidant methods commonly used for determination of antioxidant activity of components in the foodstuffs and beverages. In addition, there are given some chemical and kinetic basis and technical details of the used methods.