Antioxidants reagents

StUbenes such as resveratrol, combretastatin, and pterostUbene and their analogues possess a wide spectrum of biological activities. These compounds have been proved to be antioxidant reagents that cause cell apoptosis, suppress growing cancer cells, inhibit and activate spedfic enzymes, effed the animal aging and metabolisms... 

The CL count increased remarkably by adding samples with a small dose which does not generally affect their mechanical properties. But the amount of emission leveled off at about 50 kGy. This dose consumed the antioxidant reagent added in the production process of EP07P by energy transfer from polymer to antioxidant reagent. The detailed mechanism was reported previously [6]. 

The slope of curve in Fig. 8.3 increased at time tc. This phenomena means that the effect of small amount of antioxidant reagent which was added in the production process of EP07P to prevent oxidative degradation during storage of the sample was decreased by thermal aging and the rate of molecular chain scission increased from tc. 

The stress relaxation curves obtained at 110, 120, 130, and 140 °C are shown in Fig. 8.4. The value tc was observed in all of the decay curves [8] the time associated with tc might be comparable to the lifetime of the effect of the antioxidant reagent added in the production process. The Arrhenius plot of tc is shown in Fig. 8.5 activation energy is 116 kJ/mol. 

A small amount of antioxidant reagent added in the production process of EP07P depresses the thermal oxidation of the polymer. However, 20 h of thermal aging at 110 °C or irradiation at about 60 kGy consumed the antioxidant reagent in the sample. The rate of autoxidation at the constant temperature depends on whether the antioxidant reagent exists or not... 

Figures 8.10 and 8.11 show an increase in C=0 along with thermal aging at 60, 70, 80, 90, 100, 110, 120, 130, and 140 °C, respectively. All of the samples were irradiated up to 200 kGy there might be no antioxidant reagent in those samples.

Fig. 8.13 The effect of the concentration of antioxidant reagent on weight change of LLDPE at 150 °C...

The same result was obtained on the relationship between weight change and aging time at various temperatures ranging from 90 to 170 °C. The detail will be reported in the future. The effect of the concentration of antioxidant reagent on the... 

Fig. 8.14 Relationship between the concentration of antioxidant reagent and the induction period on the thermal aging of LLDPE at 120 °C...

Fig. 8.15 Initial sage of weight change of EP07P in which antioxidant reagent was not added at various temperatures...

Figure 8.15 shows the initial stage of weight change of LLDPE by thermal aging at varions temperatures ranging from 90 to 170 °C. The Anhenius plot of the induction period of the samples which have different concentration of antioxidant reagent was shown in Fig. 8.16. The slope of the lines was almost the same. The apparent activation energy was 136 kJ/mol.

Figure 8.17 shows the Arrhenius plot of the rate of weight increase of the sample by thermal aging. The activation energy was 105 kJ/mol, which does not appear to depend on the concentration of antioxidant reagent. 

This reason is considered as follows. The small amount of antioxidant reagent was consumed by thermal aging at this period and thermal oxidation increased. This brought about the increase in the rate of chain scission and addition of carbonyl groups. 

The relationship between weight change of LLDPE and thermal aging time is shown in Figs. 8.13 and 8.18 for the sample of nonirradiated and pre-irradiated, respectively. The irradiation shortened the induction period of the samples which contain various concentrations of antioxidant reagent. As shown in Fig. 8.18, the induction periods of all of the samples are the same. 

SOLID-PHASE REDOX REAGENTS FOR THE DETERMINATION OF BIO ANTIOXIDANTS AND TOTAL ANTIOXIDANT ACTIVITY... 

We have shown that known reaction of luminol with peroxydisulphate at low luminol concentrations takes place in the regime of controlled generation of SO ion-radicals at spontaneous destruction of peroxydisulphate. The detection limit for various types of antioxidants in water using this reaction is varied from 10 to 10 M. It is possible also to determine some polluting admixtures present in the atmosphere. The reagent used is the mixture of the luminol, base and K S O, which, once prepai ed, could be used during a working day. 

SINGLETON v L, ORTHOFER R and LAMUELA-RAVENTOS R M (1999) Analysis of total phenolics and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent, Meth Enzymol, 299, 152-78. 

Singleton, V. L., Orthofer, R., and Lamuela-Raventos, R. M. (1999). Analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. In "Methods in Enzymology, Oxidant and Antioxidants (Part A)", (L. Packer, Ed.), vol. 299 pp. 152-178. Academic Press, San Diego, CA. 

Many reagent grade solvents contain levels of impurities that make them unsuitable for long term use in hplc. Sometimes the impurities are added deliberately as antioxidants, stabilisers, or for denaturing. Wherever possible, hplc grade solvents should be used to prepare mobile phases, or alternatively the solvents should be adequately purified before use. 

Jongwon C, Keun H, Suk-Hwan K, Kyung-Tae L, Hyeong-Kyu L. Hee-Juhn P. Kalopanaxsaponin A from Kalopanax pictus, a potent antioxidant in the rheumatoidal rat treated with Freund s complete adjuvant reagent. J Ethnopharmacol 2002 79 113-118. 

---