A method for determination of fruit-derived ascorbic, tartaric, oxalic and malic acids, and its application to the study of ascorbic acid catabolism in grapevines

Abstract

Background and Aims: The majority of the acidity of a grapevine (Vitis vinifera L.) berry is a result of the accumulation of l-tartaric (TA) and l-malic acids (MA). TA is synthesised from l-ascorbic acid (Asc, vitamin C), the metabolism of which is poorly characterised in grapevines. In a distinct pathway, oxalic acid (OA) is also formed from Asc degradation. The aim of this study was to develop a single method whereby the distribution of Asc and its catabolites from fruit and vegetative sources could be determined. Methods and Results: Effective recoveries of total Asc, TA, OA and MA were achieved with this extraction method, while chromatographic separation was accomplished with reversed-phase high-performance liquid chromatography (RP-HPLC). These results demonstrate that Asc and its catabolites TA and OA rapidly accumulate in immature berries, and that the Asc to dehydroascorbate ratio increases with berry maturity. Conclusions: A method for the simultaneous analysis of Asc, TA, OA and MA in fruits is provided; moreover, we have demonstrated its use to study their distribution in fruits, rachis, leaves and roots. Significance of the Study: This method enables accurate monitoring of the accumulation of Asc, permitting further research towards understanding acid metabolism during berry ripening.