Composition and Synthesis of Raphide Crystals and Druse Crystals in Berries of Vitis vinifera L cv. Cabernet Sauvignon: Ascorbic Acid as Precursor for Both Oxalic and Tartaric Acids as Revealed by Radiolabelling Studies.

Seth De Bolt, William James Hardie, Steve Tyerman, Christopher Ford

    Research output: Contribution to journalArticlepeer-review

    47 Citations (Scopus)

    Abstract

    Biomineralisation in the fleshy pericarp of berries of Vitis vinifera L. gives rise to crystals of two distinct forms, viz. raphides and druses, which are found in exocarp and endocarp cells respectively. Druses have generally been considered as crystalline aggregates of calcium oxalate. However, the organic moiety of raphide crystals has been commonly accepted as tartrate, although we have found no analytical data to support that assumption. We now present TEM and X-ray powder diffraction analysis data showing that raphide crystals of V. vinifera berries are composed of calcium oxalate monohydrate. This work also established ascorbic acid as the biosynthetic precursor of both oxalic and tartaric acids. When ascorbic acid labelled with 14C at position 1 was introduced into berries via the rachis, 21% and 52% of the added radiolabel was recovered as oxalic and tartaric acids respectively. Purified crystals from the radiolabelled grape berries contained approximately 20% of the original radioactivity, further confirming the role of ascorbic acid in oxalic acid biosynthesis. To our knowledge, this is the first evidence to be published on the formation of oxalic and tartaric acids from ascorbic acid via two distinct pathways operating within the same physiological entity (organ).
    Original languageEnglish
    Pages (from-to)134-142
    Number of pages9
    JournalAustralian Journal of Grape and Wine Research
    Volume10
    Issue number2
    DOIs
    Publication statusPublished - 2004

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