Comparative study of antioxidant properties and cytoprotective activity of flavonoids

Our plain-English summary of Comparative study of antioxidant properties and cytoprotective activity of flavonoids, by A.I. Potapovich, V.A. Kostyuk (Biochemistry. Biokhimii︠a︡, 2003).

The study

• Authors: A.I. Potapovich, V.A. Kostyuk
• Journal: Biochemistry. Biokhimii︠a︡
• Published: 2003;68(5):514-9
• Cited by: 72 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Antioxidant properties and cytoprotective activity of flavonoids (rutin, dihydroquercetin, quercetin, epigallocatechin gallate (EGCG), epicatechin gallate (ECG)) were studied. All these compounds inhibited both NADPH- and CCl4-dependent microsomal lipid peroxidation, and the catechins were the most effective antioxidants. The I(50) values calculated for these compounds by regression analysis were close to the I(50) value of the standard synthetic antioxidant ionol (2,6-di-tert-butyl-4-methylphenol). The antiradical activity of flavonoids to O2-* was studied in a model photochemical system. Rate constants of the second order reaction obtained by competitive kinetics suggested flavonoids to be more effective scavengers of oxygen anion-radicals than ascorbic acid. By competitive replacement all flavonoids studied were shown to be chelating agents capable of producing stable complexes with transition metal ions (Fe2+, Fe3+, Cu2+). The flavonoids protected macrophages from asbestos-induced damage, and the protective effect increased in the following series: rutin < dihydroquercetin < quercetin < ECG < EGCG. The cytoprotective effect of flavonoids was in strong positive correlation with their antiradical activity to O2-*.

In plain English

This was a laboratory (test-tube) study, not a study of people. It compared five plant compounds called flavonoids: rutin, dihydroquercetin, quercetin, and two catechins, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG). The authors measured how well each compound blocked fat oxidation in rat liver microsomes, neutralized the superoxide radical, and bound iron and copper ions. They also exposed peritoneal macrophages, a type of immune cell, to chrysotile asbestos at 3 mg/ml for 20 minutes. Asbestos alone lowered reduced glutathione from 7.3 ± 2.0 to 3.1 ± 1.5 µM (p less than 0.01). It cut cell numbers from (5.5 ± 0.6) million to (1.0 ± 0.2) million cells/ml and caused release of 86 ± 12% of the enzyme LDH, a sign of cell damage. All five flavonoids reduced this damage. The concentrations needed for half protection were 275 µM for rutin, 150 for dihydroquercetin, 39 for quercetin, 12 for ECG and 10 for EGCG. Protection correlated with superoxide-scavenging activity (correlation coefficient 0.89 ± 0.24, p = 0.042), but not with metal binding. The authors suggested that the protective effect is due to this antiradical activity.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: in vitro laboratory experiment comparing antioxidant and cell-protective properties of five flavonoids
• Who was studied: no human subjects; liver microsomes isolated from rats, and suspensions of peritoneal macrophages (the species of the macrophages is not stated in this text)
• Exposure: chrysotile asbestos from the Tuva deposit (Russia), added to macrophage suspensions at 3 mg/ml for 20 minutes at 37°C; the flavonoids tested were rutin, dihydroquercetin, quercetin, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG)
• Main results:
  • In macrophages incubated with chrysotile asbestos for 20 minutes, reduced glutathione fell from 7.3 ± 2.0 to 3.1 ± 1.5 µM (p less than 0.01)
  • In the asbestos-exposed macrophages, cell numbers fell from (5.5 ± 0.6) million to (1.0 ± 0.2) million cells/ml, and release of the enzyme LDH into the medium was 86 ± 12% (p less than 0.01)
  • All flavonoids reduced asbestos-induced damage to the macrophages. The concentrations giving 50% protection (I50) were: rutin 275 µM, dihydroquercetin 150 µM, quercetin 39 µM, ECG 12 µM and EGCG 10 µM
  • The catechins EGCG and ECG protected the macrophages against lysis significantly more effectively than quercetin and dihydroquercetin, and more than 20-fold more effectively than rutin
  • Cell protection correlated directly with the rate constants for reaction with the superoxide radical (correlation coefficient 0.89 ± 0.24; regression coefficient 0.14 ± 0.04; p = 0.042). The authors found no correlation between protection and metal-binding ability
  • All five flavonoids inhibited both NADPH-dependent and CCl4-dependent lipid peroxidation in rat liver microsomes. The catechins were the strongest: I50 for NADPH-dependent peroxidation was 2.5 µM for ECG and 2.0 µM for EGCG, compared with 1.1 µM for the synthetic antioxidant ionol
  • All flavonoids except rutin scavenged the superoxide radical more effectively than ascorbic acid. Rate constants (×10^5 per M per sec) were rutin 0.5, dihydroquercetin 1.5, quercetin 1.7, ECG 3.5, EGCG 5.4 and ascorbic acid 0.7
  • When the enzyme SOD was added to asbestos-activated macrophages, oxidation of rutin was inhibited virtually completely and oxidation of quercetin by 50%
• The authors' conclusion: The authors concluded that the flavonoids had high antioxidative activity and prevented asbestos-induced damage to phagocytizing cells. They stated that the findings confirm a key role of the superoxide radical in that damage, and suggested that the protective effect of flavonoids is due to their antiradical activity toward superoxide

Topics

Medical terms in this study, explained in our Lexicon: Macrophage.

Related studies

• Antiradical and chelating effects in flavonoid protection against silica-induced cell injury — V.A. Kostyuk, A.I. Potapovich (1998)
• Influence of metal ions on flavonoid protection against asbestos-induced cell injury — V.A. Kostyuk, A.I. Potapovich, et al. (2001)
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