Showing papers by "Concepción Sánchez-Moreno published in 1998"
TL;DR: In this article, the kinetic behavior of polyphenols common in fruits as free radical scavengers was studied using 2,2-diphenyl-1-picrylhydrazyl (DPPH).
Abstract: The kinetic behaviour of polyphenols common in fruits as free radical scavengers was studied using 2,2-diphenyl-1-picrylhydrazyl (DPPH.). After addition of different standard concentrations to DPPH. (0.025 g litre-1), the percentage of remaining DPPH. was determined at different times from the absorbances at 515 nm. The percentage remaining DPPH. against reaction time followed a multiplicative model equation: In [DPPH.REM] = b 1n t + 1n a. The slopes of these equations may be useful parameters to define the antioxidant capacity. The steeper the slope, the lower the amount of antioxidant necessary to decrease by 50% the initial DPPH. concentration (EC50). This parameter, EC50, is widely used to measure antioxidant power, but it does not takes into account the reaction time. Time needed to reach the steady state to the concentration corresponding at EC50 (T(EC50)) was calculated, and antiradical efficiency (AE) was proposed as a new parameter to characterise the antioxidant compounds where AE = 1/EC50 T(EC50). It was shown that AE is more discriminatory than EC50. AE values are more useful because they also take into account the reaction time. The results have shown that the order of the AE (x 10(-3)) in the compounds tested was: ascorbic acid (11.44) > caffeic acid (2.75) greater than or equal to gallic acid (2.62) > tannic acid (0.57) greater than or equal to DL-alpha-tocopherol (0.52) > rutin (0.21) greater than or equal to quercetin (0.19) > ferulic acid (0.12) greater than or equal to 3-tert-butyl-4-hydroxyanisole, BHA (0.10) > resveratrol (0.05).
1,812 citations
TL;DR: A new classification, according to the compounds produced in the oxidation phases, is suggested as follows: measurement of oxygen absorption, conjugated dienes, peroxide values, and decomposition of lipid peroxides.
Abstract: Main spectrophotometric and chromatographic methods for determination of lipid oxidation in foods and biological systems are reviewed. A new classification, according to the compounds produced in the oxidation phases, is suggested as follows: measurement of oxygen absorption, conjugated dienes, peroxide values, and decomposition of lipid peroxides. Both conjugated dienes (propagation phase) and thiobarbituric acid (termination phase) methods are the most used, despite their interferences; however, chromatographic methods are more precise and selective. Determination of bioavailability and metabolic pathway of the antioxidants in the human body are problems to be solved in the devel opment of new biological antioxidants.
21 citations