Extraction, structural characterisation and evaluation of hydroxycinnamate esters of orchard grass (Dactylis glomerata) as substrates for polyphenol oxidase

Type Article
Original languageEnglish
Pages (from-to)2799-2806
Number of pages8
JournalPhytochemistry
Volume69
Issue number16
Early online date15 Oct 2008
DOI
Publication statusPublished - 01 Nov 2008
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Abstract

Polyphenol oxidase (PPO) activity has been reported in orchard grass (Dactylis glomerata); however, to date, no endogenous substrates have been identified. In the present study, we report the isolation and structural elucidation of PPO substrates in this species. The free phenol fraction was extracted, separated by reverse-phase chromatography and six potential substrates, including two hydroxycinnamate esters, were identified by UV spectrometry, electrospray ionisation-tandem mass spectrometry (LC?ESI-MSn) and 1D and 2D NMR analyses (1H NMR, 13C NMR, DEPT, COSY, HMQC and HMBC). Furthermore, three caffeoylquinic acids (3-CQA, 4-CQA and 5-CQA) were identified by comparison of their spectral data (ESI-MS) with those of known compounds and literature data. Five of these compounds were demonstrated to be substrates for orchard grass PPO.

Keywords

  • Dactylis glomerata, orchard grass, polyphenol oxidase, hydroxycinnamate esters, isocitric acid, hydroxycitric acid, threomic acid