DPPH radical scavenging activity of tricin and its conjugates isolated from "njavara" rice bran: A density functional theory study

Manjaly J. Ajitha, Smitha Mohanlal, Cherumuttathu H. Suresh*, Ananthasankaran Jayalekshmy

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Scopus citations

Abstract

Structural, electronic, and energetic characteristics of tricin, tricin-4′-O-(erythro-β-guaiacylglyceryl)ether (TEGE), and tricin-4′-O-(threo-β-guaiacylglyceryl)ether (TTGE), isolated from "Njavara" rice bran have been studied using DFT to explain their experimentally determined radical scavenging activity (EC 50 values) in comparison with known standards such as quercetin, myricetin, and catechin. Among the three mechanisms proposed for explaining the antioxidant activity, proton coupled-electron transfer (PC-ET), sequential proton loss electron transfer (SPLET), and electron transfer-proton transfer (ET-PT), our results support the second one. The O-H bond dissociation enthalpy (BDE) and the spin density on the oxygen with the radical character are excellent descriptors of radical scavenging activity. BDE (in kcal/mol) increased in the order myricetin (74.6) < quercetin (78.1) < catechin (78.3) < tricin (81.5) < TTGE (90.6) < TEGE (91.1), while the EC 50 increased exponentially with increase in BDE, 20.51, 42.98, 45.07, 90.39, 208.01, and 352.04 μg/mL for myricetin, quercetin, catechin, tricin, TTGE, and TEGE, respectively.

Original languageEnglish (US)
Pages (from-to)3693-3699
Number of pages7
JournalJournal of Agricultural and Food Chemistry
Volume60
Issue number14
DOIs
StatePublished - Apr 11 2012

Keywords

  • antioxidants
  • bond dissociation enthalpy
  • density functional theory
  • DPPH radical scavenging activity
  • ionization potential
  • proton affinity
  • spin density

ASJC Scopus subject areas

  • General Chemistry
  • General Agricultural and Biological Sciences

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