The total phenolic, antioxidant, radical scavenging capacities of turmeric extracts and voltammetric determination of curcuminoids

Initially, it was aimed to determine the total antioxidant capacity and the total phenolic compounds of turmeric in this thesis project. In addition, a voltammetric method was proposed for the sensitive determination of curcumin, the active ingredient of turmeric, and the validation studies of the proposed method were carried out. Firstly, Curcuma Longa L. rhizomes were powdered and extracted with two different extraction techniques. The total phenolic compounds, the total antioxidant capacity and the radical scavenging capacity in the extracts were determined spectrophotometrically using Folin-Ciocalteu, CUPRAC and DPPH methods, respectively. In the second part of the study, a voltammetric method was described to determine the amount of curcumin in turmeric rhizomes, using the glassy carbon electrode modified with multi-walled carbon nanotubes as the working electrode. The proposed method was successfully applied to determine the curcumin equivalent in a turmeric sample. In the third part of the study, the voltammetric behavior of the other curcuminoids (demetoxicurcumin and bisdemetoxicurcumin) was investigated using the validated method for curcumin.