Speciation analysis and bioaccessibility evaluation of trace elements in goji berries (Lycium Barbarum, L.)

Speciation analysis and bioaccessibility evaluation of trace elements in goji berries (Lycium Barbarum, L.)


Highlights
• A novel speciation analysis of trace metals in goji berries after in vitro simulation of gastric and gastrointestinal digestion is examined.
• SEC-ICP–MS analysis shows that Cu and Zn have high bioaccessibility for the human body.
• Among nine solutions which were used for the extraction of metal complexes from goji berries, a solutions with pectinase had the best efficiency.
• LC-ESI–MS/MS analysis was used for the identification of Cu and Zn complexes - flavonols, glycosides, carotenoids and amino acids were observed.


Abstract
Goji berries (Lycium Barbarum, L.) are known for their nutritional potential as a great source of trace metals (e.g., copper, zinc and manganese) which are present in the form of highly bioaccessible compounds. In order to assess the bioaccessibility of trace elements and to identify compounds responsible for better bioaccessibility of copper and zinc, an in vitro simulation of gastrointestinal digestion was used in this study.
The total content of trace metals was evaluated using sample digestion followed by inductively coupled plasma mass spectrometry. Bioaccessibility of trace elements was estimated by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry. These analytical methods were used to analyse samples of goji berries to determine the highest amount of elements. For total trace metal content in goji berries, Zn had the highest level of the three studied (10.6 μg g−1), while the total content of manganese and copper was 9.9 μg g−1 and 6.1 μg g−1, respectively.
Additionally, the analysed metals were found to be highly bioaccessible to the human body (about 56% for Mn, 72% for Cu and 64% for Zn in the gastric extract and approximately 35% for Mn, 23% for Cu and 31% for Zn in the case of gastrointestinal extract). To obtain information about metal complexes present in goji berries, extraction treatment using different solutions (ionic liquid, HEPES, SDS, Tris-HCl, ammonium acetate, water) was performed. Enzymatic treatment using pectinase and hemicellulase was also checked. Extracts of berries were analysed by SEC-ICP-MS and μHPLC–ESI–MS/MS techniques. The ionic liquid and pectinase extraction helped efficiently extract copper (seven compounds) and zinc (four compounds) complexes. Compounds identified in goji berries are most likely to be responsible for better bioaccessibility of those elements to the human organism.

Author information
1 Chair of Analytical Chemistry, Faculty of Chemistry, Warsaw University of Technology, Poland.
2 Chair of Analytical Chemistry, Faculty of Chemistry, Warsaw University of Technology, Poland. Electronic address: lenka@ch.pw.edu.pl.

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