Comparing Oxalic Acid Levels in Different Parts of Purslane and Spinach

Greg Howard
19th August, 2024

Comparing Oxalic Acid Levels in Different Parts of Purslane and Spinach

This figure illustrates the precipitation of calcium oxalate, a key step this study identified as essential for isolating oxalic acid from purslane (Portulaca oleracea) and spinach (Spinacea oleracea) extracts to ensure accurate quantification by removing matrix interferents.

Image adapted from: Souza et al. / CC BY (Source)

Key Findings

  • The study by Fluminense Federal University evaluated methods to measure oxalic acid in purslane and spinach
  • Methods M2 and M3, analyzed by FAAS, provided reliable and consistent oxalic acid measurements
  • UV-vis spectrophotometry showed discrepancies due to interference from colored compounds in the plant samples
Oxalic acid is a naturally occurring compound found in various plants, including purslane (Portulaca oleracea) and spinach (Spinacea oleracea). While it is a common component, oxalic acid is considered an antinutrient because it can bind to minerals like calcium and iron, reducing their bioavailability in the human body. Understanding how to accurately measure oxalic acid content in these plants is crucial for nutritional science and dietary recommendations. A recent study conducted by Fluminense Federal University[1] aimed to evaluate different methods for determining oxalic acid content in purslane and spinach. This study is significant as it addresses the challenges posed by matrix interference—where other substances in the plant samples can affect the accuracy of oxalic acid measurements. The researchers tested three extraction methods (M1, M2, and M3) and compared two analytical techniques: UV-vis spectrophotometry and Flame Atomic Absorption Spectrometry (FAAS). The study investigated different parts of purslane (whole plant, leaves, and juice) and the whole plant of spinach. The three extraction methods were designed to isolate oxalic acid with varying degrees of efficiency. Method M1, which omitted a precipitation step, resulted in high levels of oxalic acid across all samples. In contrast, methods M2 (using 6M HCl for 1 hour at 100°C) and M3 (using 0.25N HCl for 15 minutes at 100°C) produced statistically similar results when analyzed by FAAS, indicating their reliability. However, when the researchers used UV-vis spectrophotometry to measure oxalic acid, they found significant discrepancies in the results for methods M2 and M3. This inconsistency was attributed to the interference from colored compounds present in the plant matrices, which can affect the accuracy of UV-vis spectrophotometric readings. This study builds on earlier research that has explored oxalate content in different foods and the factors affecting its bioavailability. For instance, a study conducted in Christchurch, New Zealand, investigated the oxalate content in black tea and its absorption in humans[2]. The researchers found that consuming black tea with milk significantly reduced the absorption of oxalate compared to consuming tea without milk. This earlier finding highlights the importance of understanding both the oxalate content in foods and the factors that influence its bioavailability. The current study by Fluminense Federal University contributes to this body of knowledge by providing a more accurate method for measuring oxalic acid in plant matrices, which can help in assessing the dietary intake of oxalates more reliably. The use of FAAS, in particular, was shown to be less affected by matrix interference compared to UV-vis spectrophotometry, making it a more specific and reliable method for oxalic acid determination. In summary, the research conducted by Fluminense Federal University offers valuable insights into the accurate measurement of oxalic acid in purslane and spinach. By comparing different extraction methods and analytical techniques, the study highlights the importance of choosing appropriate methods to minimize matrix interference and improve the reliability of oxalic acid measurements. This work not only enhances our understanding of oxalate content in these plants but also provides a foundation for further research on the dietary impact of oxalates and their bioavailability.

VegetablesBiochemPlant Science

References

Main Study

1) Evaluation of oxalic acid extraction and quantification methods in the different purslane (Portulaca oleracea L.) matrices and spinach (Spinacea oleracea).

Published 19th August, 2024

https://doi.org/10.1016/j.mex.2024.102863

Related Studies

2) Bioavailability of soluble oxalate from tea and the effect of consuming milk with the tea.

Journal: European journal of clinical nutrition, Issue: Vol 57, Issue 3, Mar 2003


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