Rapid Colorimetric Determination of Methylglyoxal Equivalents for Manuka Honey

TH Kwok, G Kirkpatrick, HI Mohd Yusof, I Portokalakis, P Nigam, R Owusu-Apenten

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Abstract

Aims: Realization of a rapid colorimetric assay for monitoring levels of methylglyoxal and otherdicarbonyl compounds from Manuka honey.Methods: N-acetyl cysteine (NAC) and 2, 4-dinitrophenylhydrazine (DNPH) were adopted asreagents for methylglyoxal colorimetric analysis of honey at 288 or 525 nm, respectively.Results and Discussion: NAC and DNPH produced linear responses for methylglyoxal with:(i)regression coefficient (R2) equal to 0.99 or 0.97, (ii) molar absorptivity (measure of sensitivity) equal to 287±11 or 14189±498 M-1 cm-1, (iii) a minimum detectable concentration (MDC) of 0.18 mM vs 7.3 μM, (iv) upper linearity limit of linearity (ULL) equal to 4mM or 83 μM, and (v) a day-to-day precision of 16.0 and 18.3%, respectively. Low interferences occurred with reducing sugars, glyoxal or 3-deoxy-D-glucosone. For honey with a unique manuka factor (UMF) rating 5+ to UMF18+, the net concentration of dicarbonyl compounds ranged from 1069 mg-methylglyoxal equivalence per kg (mg MeGEq /kg) to 2208 (mg MeGEq /kg) using the NAC assay. For the DNPH assay, the apparent dicarbonyl concentration was 350 to 1009-mg MeGEq /kg honey. Measures of methylglyoxal equivalences were strongly correlated with the UMF rating for honeys (R2=0.98-0.99).Conclusion: The proposed colorimetric analysis of methylglyoxal equivalence in Manuka honey isfeasible proposition. Further work is needed for method validation.
Original languageEnglish
Pages (from-to)1-6
JournalJournal of Advances in Biology and Biotechnology
Volume7
Issue number1
Early online date14 Jun 2016
DOIs
Publication statusE-pub ahead of print - 14 Jun 2016

Keywords

  • Rapid determination
  • dicarbonyl compounds
  • n-acetyl cysteine
  • carbonyl reagents
  • 2
  • 4-
  • dinitrophenylhydrazine
  • methylglyoxal
  • 3-deoxy-D-glucosone
  • Advanced glycation endproducts (AGES)

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