Antioxidant phenolic constituents in roots of Rheum officinale and Rubia cordifolia: Structure-radical scavenginq activity relationships

Yizhong Cai, Mei Sun, Jie Xing, Harold Corke*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

123 Scopus citations

Abstract

The phenolic constituents in the roots of Rheum officinale and Rubia cordifolia were identified with the aid of high-performance liquid chromatography and liquid chromatography-mass spectrometry and by comparison with authentic standards. A total of 17 hydroxyanthraquinones, gallic acid, and tannins were separated, and 14 of them were identified, being the main phenolic constituents present. Their antioxidant activity (Trolox equivalent antioxidant capacity) was evaluated using the improved 2,2-azino-bis(3-ethylbenzothiazoline- 6-sulfonic acid)diammonium salt method. Hydroxyanthraquinones were the predominant antioxidant phenolic constituents in the roots of R. cordifolia, and tannins and gallic acid were the predominant antioxidant phenolic constituents in the roots of R. officinale. The structure-radical scavenging activity relationships of the tested hydroxyanthraquinones were systematically demonstrated as follows: Hydroxy groups on one benzene ring of the anthraquinone structure were essential for hydroxyanthraquinones to show activity, the ortho-dihydroxy structure in the hydroxyanthraquinone molecules could greatly enhance their radical scavenging effect, and glycosylation of the hydroxyanthraquinones reduced activity.

Original languageEnglish
Pages (from-to)7884-7890
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Volume52
Issue number26
DOIs
StatePublished - 29 Dec 2004
Externally publishedYes

Keywords

  • Anthraquinones
  • Antioxidant activity
  • Hydroxyanthraquinones
  • Phenolic constituents
  • Radical scavenging activity
  • Rheum officinale
  • Rubia cordifolia
  • Structure-activity relationships

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