Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline Solutions

The general synthesis methods of bioflavonoid–metal complexes are considered to be unreliable due to the instability of flavonoids in air-saturated alkaline solutions. In this study, dihydromyricetin (DHM), as a representative bioflavonoid, was selected for complexation with various transition metal...

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Main Authors: Yuanyong Yao, Meng Zhang, Laibing He, Yunyang Wang, Shixue Chen
Format: Article
Language:English
Published: Frontiers Media S.A. 2020-08-01
Series:Frontiers in Chemistry
Subjects:
Online Access:https://www.frontiersin.org/article/10.3389/fchem.2020.00589/full
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spelling doaj-236047a9e3764b428819445a91d12b2d2020-11-25T01:55:58ZengFrontiers Media S.A.Frontiers in Chemistry2296-26462020-08-01810.3389/fchem.2020.00589552106Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline SolutionsYuanyong YaoMeng ZhangLaibing HeYunyang WangShixue ChenThe general synthesis methods of bioflavonoid–metal complexes are considered to be unreliable due to the instability of flavonoids in air-saturated alkaline solutions. In this study, dihydromyricetin (DHM), as a representative bioflavonoid, was selected for complexation with various transition metal ions in an air-saturated alkaline solution to form DHM–metal(II) complexes, following the general synthetic procedure. After characterization, the metal complexes were hydrolyzed to observe the stability of DHM under acidic conditions via HPLC. The effects of synthetic conditions (metal ion, alkalinity, and reflux time) on DHM stability were then investigated by UV-vis spectroscopy and HPLC. Finally, using electron paramagnetic resonance, DHM and its analogs were observed with DMPO (5,5-dimethyl-1-pyrroline-N-oxide) to form a relatively stable free radical adduct. Multiple peaks corresponding to unknown compounds appeared in the LC spectra of the DHM–metal(II) complexes after hydrolysis, indicating that some DHM reacted during synthesis. Subsequently, the transition metal ion and solution alkalinity were found to have notable effects on the stability of free DHM. Furthermore, DHM and several of its analogs generated the superoxide-anion radical in air-saturated alkaline solutions. Their capacities for generating the superoxide anion seemed to correspond to the number and/or location of hydroxyl groups or their configurations. Interestingly, DHM can react with the superoxide anion to transform into myricetin, which involves the abstraction of a C3–H atom from DHM by O2−. Therefore, the general synthetic procedure for bioflavonoid–metal complexes in air-saturated alkaline solutions should be improved.https://www.frontiersin.org/article/10.3389/fchem.2020.00589/fulldihydromyricetinflavonoidsbioflavonoid–metal complexesalkaline conditionssuperoxide anionHPLC
collection DOAJ
language English
format Article
sources DOAJ
author Yuanyong Yao
Meng Zhang
Laibing He
Yunyang Wang
Shixue Chen
spellingShingle Yuanyong Yao
Meng Zhang
Laibing He
Yunyang Wang
Shixue Chen
Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline Solutions
Frontiers in Chemistry
dihydromyricetin
flavonoids
bioflavonoid–metal complexes
alkaline conditions
superoxide anion
HPLC
author_facet Yuanyong Yao
Meng Zhang
Laibing He
Yunyang Wang
Shixue Chen
author_sort Yuanyong Yao
title Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline Solutions
title_short Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline Solutions
title_full Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline Solutions
title_fullStr Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline Solutions
title_full_unstemmed Evaluation of General Synthesis Procedures for Bioflavonoid–Metal Complexes in Air-Saturated Alkaline Solutions
title_sort evaluation of general synthesis procedures for bioflavonoid–metal complexes in air-saturated alkaline solutions
publisher Frontiers Media S.A.
series Frontiers in Chemistry
issn 2296-2646
publishDate 2020-08-01
description The general synthesis methods of bioflavonoid–metal complexes are considered to be unreliable due to the instability of flavonoids in air-saturated alkaline solutions. In this study, dihydromyricetin (DHM), as a representative bioflavonoid, was selected for complexation with various transition metal ions in an air-saturated alkaline solution to form DHM–metal(II) complexes, following the general synthetic procedure. After characterization, the metal complexes were hydrolyzed to observe the stability of DHM under acidic conditions via HPLC. The effects of synthetic conditions (metal ion, alkalinity, and reflux time) on DHM stability were then investigated by UV-vis spectroscopy and HPLC. Finally, using electron paramagnetic resonance, DHM and its analogs were observed with DMPO (5,5-dimethyl-1-pyrroline-N-oxide) to form a relatively stable free radical adduct. Multiple peaks corresponding to unknown compounds appeared in the LC spectra of the DHM–metal(II) complexes after hydrolysis, indicating that some DHM reacted during synthesis. Subsequently, the transition metal ion and solution alkalinity were found to have notable effects on the stability of free DHM. Furthermore, DHM and several of its analogs generated the superoxide-anion radical in air-saturated alkaline solutions. Their capacities for generating the superoxide anion seemed to correspond to the number and/or location of hydroxyl groups or their configurations. Interestingly, DHM can react with the superoxide anion to transform into myricetin, which involves the abstraction of a C3–H atom from DHM by O2−. Therefore, the general synthetic procedure for bioflavonoid–metal complexes in air-saturated alkaline solutions should be improved.
topic dihydromyricetin
flavonoids
bioflavonoid–metal complexes
alkaline conditions
superoxide anion
HPLC
url https://www.frontiersin.org/article/10.3389/fchem.2020.00589/full
work_keys_str_mv AT yuanyongyao evaluationofgeneralsynthesisproceduresforbioflavonoidmetalcomplexesinairsaturatedalkalinesolutions
AT mengzhang evaluationofgeneralsynthesisproceduresforbioflavonoidmetalcomplexesinairsaturatedalkalinesolutions
AT laibinghe evaluationofgeneralsynthesisproceduresforbioflavonoidmetalcomplexesinairsaturatedalkalinesolutions
AT yunyangwang evaluationofgeneralsynthesisproceduresforbioflavonoidmetalcomplexesinairsaturatedalkalinesolutions
AT shixuechen evaluationofgeneralsynthesisproceduresforbioflavonoidmetalcomplexesinairsaturatedalkalinesolutions
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