High and low oxalate content in spinach: an investigation of accumulation patterns

Abstract

BACKGROUND Oxalic acid is a common antinutrient in the human diet, found in large quantities in spinach. However, spinach is highly regarded by vegetable producers because of its nutritional content and economic value. One of the primary purposes of spinach‐breeding programs is to improve the nutritional value of spinach by adjusting oxalate accumulation. Knowledge of the biosynthetic patterns of oxalic acid, and its different forms, is important for a better understanding of this process. RESULTS We found three biosynthetic patterns of accumulation and concentration of oxalates. Two of them are related to the maximum type and one is related to the minimum type. We also developed a general model of variations in these compounds in the genotypes that were studied. CONCLUSION This study introduced a unique type of spinach with high oxalate accumulation, which could be particularly suitable for consumption. This had the highest ratio of insoluble oxalate to soluble oxalate. It also accumulated more ascorbic acid (AA) than other types. Our findings in this study also indicate a small role for AA as a precursor to oxalate production in spinach, possibly confirming the significant role of glyoxylate as the most critical precursor in this plant. © 2021 Society of Chemical Industry.

Oxalate in Plants: Metabolism, Function, Regulation, and Application

“…23 Recently, by investigating the accumulation patterns of oxalic acid in spinach varieties with different oxalic acid contents, it was found that ascorbic acid can significantly increase the proportion of insoluble oxalate to total oxalic acid but contributes little to oxalate biosynthesis. 35 These contradictory results suggest that ascorbic acid may have different roles in oxalic acid biosynthesis in different plant species. Direct molecular genetic evidence is required to further support the role of ascorbic acid in oxalate biosynthesis.…”

“… By contrast, repressed expression of l -galactono-1,4-lactone dehydrogenase (GLDH) gene encoding enzyme that catalyzes the last step of the ascorbic acid synthesis pathway significantly reduced the ascorbic acid content in rice but did not decrease the oxalic acid content . Recently, by investigating the accumulation patterns of oxalic acid in spinach varieties with different oxalic acid contents, it was found that ascorbic acid can significantly increase the proportion of insoluble oxalate to total oxalic acid but contributes little to oxalate biosynthesis . These contradictory results suggest that ascorbic acid may have different roles in oxalic acid biosynthesis in different plant species.…”