Sixième Colloque International Sciences & Environnement Antioxidant activity study of novel hybrid cyclohexaphosphates and comparison of obtained results in the different materials Ramzi Fezai(a), Ali Mezni(b) and Mohamed Rzaigui(a) (a)Laboratoire de chimie des matériaux, Faculté des Sciences de Bizerte, 7021 Zarzouna, Université de Carthage Tunisie (b) Laboratoire des substances bio-actives, Faculté des Sciences de Bizerte 7021 Zarzouna, Université de Carthage, Tunisie INTRODUCTION Recently, scientists are interested in new compounds, either synthesized or obtained from natural sources, which could exhibit an ability to prevent or reduce the impact of oxidative stress on cells. In the present communication, we report the antioxidant activity study, in vitro, as a function of the concentration (0.25, 0.5 and 1 mg/mL) of a series of new synthesized organic cyclohexaphosphates and a brief comparison of obtained results. ½ Li2CO3 + H3PO4 LiH2PO4 + ½ (CO2 + H2O) 6 LiH2PO4 + 0.1 Li6P6O18 1.1 Li6P6O18 + 6H2O Li6P6O18.6H2O Cation-exchange resin H6P6O18 + Amines Organic Cyclohexaphosphates Chemical Synthesis: Abreviations AA : Ascorbic acid, o-OMe : [o-(OCH3)C6H4NH3]4H2P6O18.4H2O, 2,3-DMA : [2,3-(CH3)2C6H3NH3]6P6O18.2H2O 4-F : [p-(F)C6H4NH3]6P6O18.2H2O p-ɸ : [p-(NH3)C6H4NH3]3P6O18.6H2O DPPH free radical scavenging activity The increase of the concentration state an increase in the inhibition percentage of DPPH radicals. All materials show a significant ability to scavenge DPPH radicals. The o-OMe material exhibits the important inhibition compared to others organic cyclohexaphosphates. The scavenging activity is due to the richness in oxygen and nitrogen atoms involved as donors and acceptors in the tridimensional H- bonding network. Comparison of DPPH radical scavenging activity in the different materials at 1mg/mL DPPH radical scavenging activity as a function of the concentration in the different materials Degradation of deoxyribose (Fenton’s reaction) The studied organic cyclohexaphosphates show significant ability to scavenge OH radicals with compare to ascorbic acid. The higher percentage is observed in the o- OMe material with 91% (IC50 = 0.43 mg/mL). While the p-ϕ compound exhibits the smallest inhibition with 76% and IC50 = 0.49 mg/mL. These observed values are very close to that of ascorbic acid (96% and IC50 = 0.43 mg/mL) excepting p-ϕ compound. OH radical scavenging ability as a function of the concentration in the different materials Comparison of OH radical scavenging ability in the different materials at 1mg/mL Reducing power The synthesized materials show moderate reducing power compared to ascorbic acid. The highest percentage is observed in the o- OMe material. The least reducer compound is the p-ϕ with 48%. The reducing power is inversely proportional to the IC50 value; 0.79 for the o-OMe, 0.88 for the 2,3-DMA, 0.76 for the 4-F and 1.08 mg/mL for the p-ϕ compound. Reducing power assay as a function of the concentration in the different materials. Comparison of the reducing power assay in the different materials at 1mg/mL Ferrous ion chelating ability Results show that these organic cyclohexaphosphates are not good chelator of ferrous ion, excepting the o-OMe which exhibits an inhibition with 75% and IC50 = 0.57 mg/mL compared to ascorbic acid at the same concentration 80% and IC50 = 0.53 mg/mL. The p-ϕ compound shows also a moderate inhibition with 38% and IC50 = 1.11 mg/mL. Ferrous ion chelating (FIC) ability as a function of the concentration in the different materials. Comparison of ferrous ion chelating (FIC) ability in the different materials at 1mg/mL CONCLUSION These hybrid compounds possesses significant scavenging capacity of free radicals (DPPH• and OH•) compared to the ascorbic acid and a moderate reducing power and ferrous ion chelating ability. The proton-diffusion ability could explain the behavior of these materials as free radical inhibitors or scavengers, acting possibly as primary antioxidants.