Synthesis and Antioxidant Activity of Rosmariquinone and Several Analogues

Clifford A. Hall, Susan L. Cuppett, Pat Dussault

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Rosmariquinone (1) and six analogues were chemically synthesized using an ultrasound-promoted Diels - Alder cycloaddition in yields of 35-90%. The analogues included substitution of the isopropyl at carbon 13 (C-13) with a hydrogen (5), methyl (6), or tert-butyl (4) substituent. The hydrogen-substituted analogue had the lowest yield at 35%, due in part to the instability of the compound to air, while the highest yields were achieved for the methyl (85%) and tert-butyl (90%) analogues. The 60% yield obtained for the C-14 methyl analogue (7; no C-13 isopropyl) may have been caused by the meta-substituted catechol inhibiting the cycloaddition. The final two analogues were ring A modifications and included the removal of one C-4 methyl (3; 80% yield) or both C-4 methyl (2; 85% yield) groups. The analogues were tested against rosmariquinone in light-sensitized oxidation of stripped soybean oil. Analogues 5 and 6 were significantly (P < 0.05) better antioxidants than rosmariquinone and all other analogues. The antioxidant properties of compounds 2-7 were not significantly different (P < 0.05) from each other while compounds 2 and 4 had significantly (P < 0.05) lower antioxidant activity than rosmariquinone. This study demonstrated the importance of structural characteristics of antioxidants and that natural antioxidants, such as rosmariquinone, can be improved through chemical modification.

Original languageEnglish (US)
Pages (from-to)1303-1310
Number of pages8
JournalJournal of Agricultural and Food Chemistry
Volume46
Issue number4
DOIs
StatePublished - Apr 1998

Keywords

  • Antioxidant activity
  • Diels-Alder cycloaddition
  • Rosmariquinone
  • Ultrasound

ASJC Scopus subject areas

  • Chemistry(all)
  • Agricultural and Biological Sciences(all)

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