Investigation Of Beta-carotene Atmospheric Oxidation Process In The Anionic Surfactant System In Absence And Presence Of Vitamin C
INVESTIGATION OF BETA-CAROTENE ATMOSPHERIC OXIDATION PROCESS IN THE ANIONIC SURFACTANT SYSTEM IN ABSENCE AND PRESENCE OF VITAMIN C
M. Szymula
Department Radiochemistry and Colloid Chemistry, Faculty of Maria Curie-Sklodowska University, Maria Curie-Sklodowska sq. 3, 20-031 Lublin, Poland
b-Carotene is a very efficient antioxidant acting as the most important physiological quencher, which protects cells against singlet oxygen damage.
It is well known that the antioxidant activity of antioxidant substances in homogenous solutions may not be the same as that in heterogeneous media.
This matrix dependence is the reason for our study of b-carotene in micelles in which it can be arranged in an ordered way. In addition to this ordered environment, micelles also provide an interface of a hydrophilic and a hydrophobic region. This interface can be a simple model for studying the processes occurring in biological membranes.
In the present paper, we described the atmospheric oxidation of b-carotene in anionic surfactant as well as the role that the ascorbic acid presence plays towards b-carotene antioxidant action.
Our investigations are based on a well-known pentanol/ water/ sodium dodecyl sulphate micellar system. It contains the inverse micellar solution, the basis for W/O microemulsions, a bicontinous part, and the aqueous micellar solution that forms the basis for the O/W microemulsions.
The kinetics of b-carotene and the ascorbic acid decomposition in the system were determined by ultraviolet spectroscopy.
As can be expected b-carotene is more stable in W/O microemulsion than in O/W one. In micelles, the long conjugated hydrocarbon chain of b-carotene is located in the hydrophobic region, but its terminal polar group may be in contact with water and subject to oxidation. Vitamin C addition into the system does not change antioxidant properties of b-carotene which is still a better antioxidant in the O/W microemulsion.
A very interesting conclusion is that the b-carotene presence strongly influences vitamin C antioxidant action. The vitamin C antioxidant capability
increases with the decrease of pentanol concentration in the system containing b-carotene (i.e. in O/W microemulsion). These results are different from the results presented earlier. Vitamin C is a better antioxidant in the W/O microemulsion than in the O/W one (M. Szymula, J. Szczypa, S.E. Friberg, J.Dispersion Science and Technology, in press). Addition of vitamin C to the anionic surfactant system changes the region of vitamin E antioxidant activity. In the presence of vitamin C, vitamin E is a better antioxidant in the W/O microemulsion, while in the absence of vitamin C it is a better antioxidant in the O/W one (M. Szymula, Atmospheric Oxidation of Vitamin C and E in the Surfactant System, J. Dispersion Science and Technology, 21, (7), 983-998, 2000).
Significant antioxidant synergism and novel mutual protection of b-carotene and vitamin C was found in the anionic surfactant system.
One should recall that what has been observed in vitro, may not be automatically transferred to the living system.
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