Determination of Total Content of Phenolic Compounds and Their Antioxidant Activity in VegetablesEvaluation of Spectrophotometric Methods

Abstract

This research studies in detail the contents of phenolic compounds determined by the Folin-Ciocalteu reagent and the antioxidant activities determined by the TEAC (Trolox equivalent antioxidant capacity), DPPH (using diphenyl-p-picrylhydrazyl radical), and FRAP (ferric reducing antioxidant power) methods, and their correlations for used standards with these methods (catechine, gallic acid, caffeic acid, ferulic acid, Trolox, ascorbic acid, and ferrous sulfate) and extracts from several species of commonly consumed vegetables were studied in detail. The comparison of absolute values of absorption coefficients for used standards and for individual methods allows one to choose optimal common standards for methods to be compared. The procedures applied for the same sets of the extracts using identical calibration procedures and common standards allowed better comparison of the results obtained by the TEAC, DPPH, and FRAP methods. The values of content of phenolic substances and total antioxidant activity of the sets of samples correlate very well for all used methods. The very high values of antioxidant activity were found in intensely colored vegetables (red cabbage, red onion, etc.), and the values were very low in watery vegetables such as potato, marrow, and cucumber.

Theoretical Study of the Hydrogenation Reactions between 1,2-diazene and Flavonoid Molecules

“…So we can say that the compound 3b (2R3R) is the thermodynamic product and compound 3'b(2S 3S) is the kinetic product of Our theoretical results clearly confirm the existence of stereoisomere 3b that is thermodynamically more stable than stereoisomeres 3'b(2S 3S), 3b 1 (2S 3R) and 3b 2 (2R3S). This explains well the existence of flavanone 3b in different plants [1][2][3][4] .…”

“…This confirms the existence of flavanone 3a(2R). However the existence of compound 3'a(2S) is not possible in nature [1][2][3][4] . Second, we determine the transition states of reaction between (Z)-1,2-diazene 2 and flavonol 1b in both approaches endo and exo.…”

Flavonoids and phenolic acids from pearl millet (Pennisetum glaucum) based foods and their functional implications

“…Tricin is abundant in millet, oats, and wheat. Tricin has been shown to have anticancer effects in the lower gut [42]. Moreover, Tricin has a relaxant effect on smooth muscle of intestinal tissues, powerful antioxidant effects [43], potent antihistaminic activity [44], and growth inhibition of human malignant breast tumor cells and colon cancer cells [45][46].…”

Comparison of the phenolic content and total antioxidant activity in wines as determined by spectrophotometric methods

“…The differences could be caused, above all, by the different reaction times used in the experiments. The authors used a very short incubation time (only 3 min) that corresponded to about one third to one half of the reaction time since the reaction can proceed for up to much as 30 minutes (Stratil et al 2006). Fernández-Pachón et al (2006) presented the values of TEAC in the range from 0.14 to 1.45 mmol/l TE for white wines (n = 13).…”

“…According to our measurement, the increase was equal to 0.980, 0.340, 0.084, 0.560, and 0.730 absorbance units for FCM, PBM, TEAC, FRAP, and DPPH methods, respectively. The parameters of the calibration equations of the methods for ascorbic acid were published in our previous paper (Stratil et al 2006).…”