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Prooxidant and antioxidant roles of ...

Zhang, Peng.

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Prooxidant and antioxidant roles of beta-carotene, alpha-tocopherol, ascorbic acid.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Prooxidant and antioxidant roles of beta-carotene, alpha-tocopherol, ascorbic acid./
Author:	Zhang, Peng.
Description:	185 p.
Notes:	Adviser: Stanley T. Omaye.
Contained By:	Dissertation Abstracts International61-09B.
Subject:	Health Sciences, Nutrition. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9985733
ISBN:	059992439X

Prooxidant and antioxidant roles of beta-carotene, alpha-tocopherol, ascorbic acid.
Zhang, Peng.

Prooxidant and antioxidant roles of beta-carotene, alpha-tocopherol, ascorbic acid. - 185 p.

Adviser: Stanley T. Omaye.

Thesis (Ph.D.)--University of Nevada, Reno, 2000.

Oxidative damage in biologic systems may occur in the presence of high levels of reactive oxygen species (ROS) produced during normal metabolism and in inflammation. ROS can oxidize particular target molecules in living cells (e.g., lipid, protein, and DNA) and may also be implicated in aging and other degenerative diseases, including cancer and cardiovascular diseases. The potential for β-carotene to modulate oxidative damage has been questioned since three major intervention trials showed a lack of protective effect of β-carotene supplements against lung cancer. Increasing evidence shows that the antioxidant activity of β-carotene may shift into prooxidant activity depending on the redox potential of β-carotene molecule as well as on the biologic environment in which it acts. This study evaluates the effect of β-carotene on protection of biologic systems (isolated lipid, protein, DNA, and human lung cell line) against oxidative stress induced by free radical initiators. The relationship of β-carotene concentration, oxygen tension, other antioxidant vitamins, and source of free radical initiator has also been examined. The results showed that β-carotene exhibited an antioxidant effect at low oxygen tension and a prooxidant effect at high oxygen tension in all models. Both antioxidant and prooxidant effects are dose-dependent. β-Carotene causes concentration dependent lipid peroxidation, protein oxidation and DNA breakdown at high O2 tension. α-Tocopherol and ascorbic acid exhibited provided dose dependent protection under low O2 tension in all models. The mixture of β-carotene with other vitamins (vitamin C and E) showed a better protection of these biologic models from oxidation. β-carotene works better in lipid-soluble environment as an antioxidant. Oxygen tension seems to play an important role in determining the effect of β-carotene in biologic systems. The products of β-carotene directly responsible for the prooxidant activity have not been identified yet. Data from in vitro studies need to be verified in vivo before any decision is made for disease prevention.

ISBN: 059992439XSubjects--Topical Terms:

1017801
Health Sciences, Nutrition.

Prooxidant and antioxidant roles of beta-carotene, alpha-tocopherol, ascorbic acid.
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100 1 $a Zhang, Peng. $3 1259627
245 1 0 $a Prooxidant and antioxidant roles of beta-carotene, alpha-tocopherol, ascorbic acid.
300 $a 185 p.
500 $a Adviser: Stanley T. Omaye.
500 $a Source: Dissertation Abstracts International, Volume: 61-09, Section: B, page: 4657.
502 $a Thesis (Ph.D.)--University of Nevada, Reno, 2000.
520 $a Oxidative damage in biologic systems may occur in the presence of high levels of reactive oxygen species (ROS) produced during normal metabolism and in inflammation. ROS can oxidize particular target molecules in living cells (e.g., lipid, protein, and DNA) and may also be implicated in aging and other degenerative diseases, including cancer and cardiovascular diseases. The potential for β-carotene to modulate oxidative damage has been questioned since three major intervention trials showed a lack of protective effect of β-carotene supplements against lung cancer. Increasing evidence shows that the antioxidant activity of β-carotene may shift into prooxidant activity depending on the redox potential of β-carotene molecule as well as on the biologic environment in which it acts. This study evaluates the effect of β-carotene on protection of biologic systems (isolated lipid, protein, DNA, and human lung cell line) against oxidative stress induced by free radical initiators. The relationship of β-carotene concentration, oxygen tension, other antioxidant vitamins, and source of free radical initiator has also been examined. The results showed that β-carotene exhibited an antioxidant effect at low oxygen tension and a prooxidant effect at high oxygen tension in all models. Both antioxidant and prooxidant effects are dose-dependent. β-Carotene causes concentration dependent lipid peroxidation, protein oxidation and DNA breakdown at high O2 tension. α-Tocopherol and ascorbic acid exhibited provided dose dependent protection under low O2 tension in all models. The mixture of β-carotene with other vitamins (vitamin C and E) showed a better protection of these biologic models from oxidation. β-carotene works better in lipid-soluble environment as an antioxidant. Oxygen tension seems to play an important role in determining the effect of β-carotene in biologic systems. The products of β-carotene directly responsible for the prooxidant activity have not been identified yet. Data from in vitro studies need to be verified in vivo before any decision is made for disease prevention.
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