, Volume 47, Issue 6, pp 493–502 | Cite as

Potential thermodynamic and kinetic roles of phytate as an inhibitor of kidney stone formation: theoretical modelling and crystallization experiments

  • Saajidah Fakier
  • Allen RodgersEmail author
  • Graham Jackson
Original Paper


Kidney stone formation is governed by thermodynamic (supersaturation) and kinetic (crystal nucleation, growth, aggregation) mechanisms. We adopted a dual theoretical and experimental approach to investigate the potential role of urinary phytate in this regard. Thermodynamic constants for eight protonated phytate species and seven calcium–phytate complexes were determined by potentiometry and incorporated into the speciation program JESS. Urine was collected from 16 heathy males and their urine compositions were used as input for JESS. Phytate concentration was varied during modelling. No statistically significant decreases in Ca2+ concentrations or in supersaturation values were predicted by JESS. Crystallization experiments were then performed in pooled urine. Endogenous phytate concentration was determined using a metal–dye assay. The pool was dosed with various concentrations of phytate to achieve final concentrations equivalent to those used for modelling. Experiments showed that phytate had no effects on Ca2+ concentrations (as predicted by our theoretical modelling), metastable limits or crystal nucleation and growth kinetics. However, crystal aggregation kinetics was inhibited. We speculate that HPhy−11, small amounts of which were revealed by modelling, may bind to crystal surfaces and inhibit aggregation. We conclude that phytate exerts a kinetic, but not a thermodynamic inhibitory effect on crystallization in urine.


Speciation modelling Calcium–phytate complexation Urinary crystallization Aggregation inhibition Calcium stone formation 



Major sections of the work described in this paper are based on studies performed by the first author Saajidah Fakier as part of her Ph.D. thesis [33]. The authors wish to thank the South African National Research Foundation, the South African Medical Research Council and the University of Cape Town for financial support.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.

Ethical approval

All procedures performed in human studies were approved by the Human Research Ethics Committee of the University of Cape Town (HREC REF: 072/2014) and were performed in accordance with the ethical standards of the 1964 Helsinki Declaration and its later amendments.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Supplementary material

240_2019_1117_MOESM1_ESM.docx (17 kb)
Supplementary material 1 (DOCX 17 KB)
240_2019_1117_MOESM2_ESM.docx (14 kb)
Supplementary material 2 (DOCX 13 KB)


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© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.1Department of ChemistryUniversity of Cape TownCape TownSouth Africa

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