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A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
Published on: April 11, 2014
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A role for ascorbate conjugates of (+)-catechin in proanthocyanidin polymerization
Keji Yu1,2, Richard A Dixon3, Changqing Duan4,5
1Center for Viticulture and Enology, College of Food Science & Nutritional Engineering, China Agricultural University, Beijing, 100083, China.
Nature Communications
|June 14, 2022
Summary
Ascorbate (AsA) acts as a novel starter unit for proanthocyanidin (PA) formation, forming unique conjugates. These "sub-PAs" reveal a new pathway for PA oligomerization beyond sequential monomer addition.
Area of Science:
- Plant biochemistry
- Natural product chemistry
- Molecular genetics
Background:
- Proanthocyanidins (PAs) are vital plant polymers derived from flavan-3-ols like (+)-catechin.
- The precise mechanisms governing PA oligomerization remain largely unknown.
Purpose of the Study:
- To elucidate the initial steps and intermediates in (+)-catechin-type proanthocyanidin biosynthesis.
- To investigate the role of ascorbate in PA formation.
Main Methods:
- Biochemical assays and genetic analysis in Arabidopsis thaliana (ans mutant).
- Metabolite profiling in Arabidopsis and Vitis vinifera (grape).
- In vitro polymerization studies.
Main Results:
- Ascorbate (AsA) serves as an alternative starter unit to flavan-3-ols for (+)-catechin subunit extension.
- Novel ascorbate-(catechin)n conjugates (AsA-[C]n), termed "sub-PAs", were identified.
- Sub-PAs can provide PA extension units for non-enzymatic polymerization in vitro.
Conclusions:
- PA oligomerization can initiate with ascorbate, not solely flavan-3-ol monomers.
- AsA-[C]n represents a new class of PA intermediates, expanding understanding of PA biosynthesis.
- This discovery challenges the paradigm of sequential monomer addition in PA extension.
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