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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
Ascorbic acid conjugates isolated from the phloem of Cucurbitaceae
Robert D Hancock1, John A Chudek, Paul G Walker
1Scottish Crop Research Institute, Plant Products and Food Quality, Invergowrie, Dundee DD2 5DA, United Kingdom. Rob.Hancock@scri.ac.uk
Phytochemistry
|May 13, 2008
Summary
Researchers identified l-ascorbic acid conjugates in Cucurbitaceae phloem, with 6-O-glucosyl-l-ascorbic acid being the most abundant. These findings suggest a role for these conjugates in the long-distance transport of vitamin C in plants.
Area of Science:
- Plant Physiology
- Biochemistry
- Phloem Transport
Background:
- l-ascorbic acid (vitamin C) is essential for plant growth and stress response.
- Understanding the transport mechanisms of essential compounds in plants is crucial for agricultural science.
- Previous research has not fully elucidated the forms of l-ascorbic acid transported in plant phloem.
Purpose of the Study:
- To identify and characterize compounds with UV-visible absorption spectra similar to l-ascorbic acid in Cucurbitaceae phloem exudates.
- To determine the chemical structure of the major l-ascorbic acid conjugate found in Cucurbita pepo L. phloem.
- To discuss the potential role of identified l-ascorbic acid conjugates in long-distance plant transport.
Main Methods:
- Analysis of phloem exudates from Cucurbitaceae fruit using UV-visible spectroscopy.
- Isolation and purification of compounds using strong anion exchange chromatography.
- Enzymatic oxidation studies with ascorbate oxidase.
- Mass spectrometry (MS) and Nuclear Magnetic Resonance (NMR) spectroscopy for structural elucidation.
- Acid hydrolysis to determine constituent components.
Main Results:
- Compounds with UV-visible spectra identical to l-ascorbic acid were detected in Cucurbitaceae phloem exudates.
- These compounds were absent in whole tissue homogenates of Cucurbita pepo L., indicating phloem-specific presence.
- The major identified conjugate, 6-O-glucosyl-l-ascorbic acid (6-GlcAsA), was structurally characterized by MS, NMR, and hydrolysis, showing distinct properties from other isomers.
- 6-GlcAsA exhibited similar redox properties to l-ascorbic acid and synthetic 6-GlcAsA.
Conclusions:
- A series of l-ascorbic acid conjugates, primarily 6-O-glucosyl-l-ascorbic acid, have been identified in the phloem of Cucurbitaceae.
- The study provides evidence for the presence and structure of these conjugates, suggesting they are involved in l-ascorbic acid transport.
- Further research is warranted to fully understand the physiological significance and transport dynamics of these conjugates in plants.
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