Speciation of essential nutrient trace elements in coconut water

Food Chem. 2021 Mar 1:339:127680. doi: 10.1016/j.foodchem.2020.127680. Epub 2020 Aug 5.

Abstract

Coconut water (Cocos Nucifera) is shown to be a source of essential elements present in the form of low-molecular weight stable complexes known for their bio-availability. The total element concentrations were in the range of 0.2-2.7, 0.3-1, 3-14 and 0.5-2 ppm for Fe, Cu, Mn, and Zn, respectively, and varied as a function of the origin of the nut and its maturity. Speciation was investigated by size-exclusion chromatography - inductively coupled plasma mass spectrometry (ICPMS), and hydrophilic interaction liquid chromatography (HILIC) - electrospray-OrbitrapMS. The metal species identified included: iron complexes with citrate and malate: FeIII(Cit)3(Mal), FeIII(Cit)2(Mal)2, FeIII(Mal)2, glutamine: FeIII(Glu)2 and nicotianamine: FeII(NA); copper complexes with phenylanine: CuII(Phe)2 and CuII(Phe)3 and nicotianamine: CuII(NA); zinc complexes with citrate: ZnII(Cit)2 and nicotianamine ZnII(NA) and manganese complex with asparagine MnII(Asp)2. The contributions of the individual species to the total elements concentrations could be estimated by HILIC - ICP MS.

Keywords: Coconut water; ESI MS; HILIC; Low-molecular weight complexes; SEC-ICP MS; Speciation; Trace elements.

MeSH terms

  • Azetidinecarboxylic Acid / analogs & derivatives
  • Azetidinecarboxylic Acid / analysis
  • Azetidinecarboxylic Acid / chemistry
  • Chromatography, Gel
  • Chromatography, Liquid
  • Citric Acid / analysis
  • Citric Acid / chemistry
  • Cocos / chemistry*
  • Food Analysis / methods
  • Fruit and Vegetable Juices / analysis*
  • Malates / analysis
  • Malates / chemistry
  • Metals / analysis*
  • Metals / chemistry
  • Molecular Weight
  • Spectrometry, Mass, Electrospray Ionization
  • Trace Elements / analysis*
  • Trace Elements / chemistry*

Substances

  • Malates
  • Metals
  • Trace Elements
  • Citric Acid
  • nicotianamine
  • Azetidinecarboxylic Acid
  • malic acid