Ferric citrate or iron(III) citrate describes any of several complexes formed upon binding any of the several conjugate bases derived from citric acid with ferric ions. Most of these complexes are orange or red-brown. They contain two or more Fe(III) centers.[3]

Ferric citrates contribute to the metabolism of iron by some organisms. Citrates, which are released by plant roots and by some microorganisms, can solubilize iron compounds in the soil. For example ferric hydroxide reacts with citrates to give form soluble complexes. This solubilization provides a pathway for the absorption of the ferric ions by various organisms.[4]

Ferric citrate is used in medicine to regulate the blood levels of iron in patients with chronic kidney disease on dialysis. It acts by forming an insoluble compound with phosphate present in the diet and thus minimizing its uptake by the digestive system.[5]

Structure

Citrate forms a variety of coordination complexes with ferric ions.[6][1] Some might be oligomers, and polymers. Thus, ferric citrate is not a single well-defined compound, but a family of compounds, many with similar formulas. These various forms can coexist in equilibrium.[7] At physiological pH, ferric citrate forms an insoluble red polymer. In other conditions, it forms anionic complexes like [FeC
6H
4O
7]2(H
2O)2]2−. In the presence of excess citrate anions, the iron forms negatively charged complexes like [Fe(C
6H
4O
7)2]5− and [Fe
9O(C
6H
4O
7)8(H
2O)3]7−.[3][4]

Photoreduction

The Fe3+
 ion in ferric citrate (as in many iron(III) carboxylates) is reduced by exposure to light,[8] especially blue and ultraviolet, to Fe2+
 (ferrous) ion with concomitant oxidation of the carboxyl group adjacent to the hydroxyl, yielding carbon dioxide and acetonedicarboxylate:

2Fe3+
 + R2-C(OH)-CO−
2 → 2Fe2+
 + R2-C=O + H+
 + CO
2

where -R represents the group -CH
2CO−
2. This reaction plays an important role in plant metabolism: iron is carried up from the roots as ferric citrate dissolved in the sap,[9] and photoreduced in the leaves to iron(II) that can be transported into the cells.

Additional reading

Abrahamson HB, Rezvani AB, Brushmiller J (1994). "Photochemical and Spectroscopic Studies of Complexes, of Iron(III) with Citric Acid and Other Carboxylic Acids". Inorganica Chimica Acta. 226 (1–2): 117–127. doi:10.1016/0020-1693(94)04077-X.

Society and culture

In March 2025, the Committee for Medicinal Products for Human Use of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Xoanacyl, intended for the treatment of concomitant hyperphosphatemia and iron deficiency in adults with chronic kidney disease.[10] The active substance of Xoanacyl is ferric citrate coordination complex.[10] The applicant for this medicinal product is Averoa SAS.[10]

References

  1. ^ a b Shweky I, Bino A, Goldberg DP, Lippard SJ (1994). "Syntheses, Structures, and Magnetic Properties of Two Dinuclear Iron(III) Citrate Complexes". Inorganic Chemistry. 33 (23): 5161–5162. doi:10.1021/ic00101a001.
  2. ^ Sigma-Aldrich: Product Specification - Iron(III) citrate, technical grade. Accessed on 2017-03-09.
  3. ^ a b Bino A, Shweky I, Cohen S, Bauminger ER, Lippard SJ (1998). "A Novel Nonairon(III) Citrate Complex: A "Ferric Triple-Decker"". Inorganic Chemistry. 37 (20): 5168–5172. doi:10.1021/ic9715658.
  4. ^ a b Pierre JL, Gautier-Luneau I (2000). "Iron and Citric Acid: A Fuzzy Chemistry of Ubiquitous Biological Relevance". Biometals. 13 (1): 91–96. doi:10.1023/A:1009225701332. PMID 10831230. S2CID 2301450.
  5. ^ Lewis JB, Sika M, Koury MJ, Chuang P, Schulman G, Smith MT, et al. (2015). "Ferric Citrate Controls Phosphorus and Delivers Iron in Patients on Dialysis". Journal of the American Society of Nephrology. 26 (2): 493–503. doi:10.1681/ASN.2014020212. PMC 4310662. PMID 25060056.
  6. ^ Xiang Hao, Yongge Wei, Shiwei Zhang (2001): "Synthesis, crystal structure and magnetic property of a binuclear iron(III) citrate complex". Transition Metal Chemistry, volume 26, issue 4, pages 384–387. doi:10.1023/A:1011055306645
  7. ^ Silva AM, Kong X, Parkin MC, Cammack R, Hider RC (2009). "Iron(III) citrate speciation in aqueous solution". Dalton Transactions (40): 8616–25. doi:10.1039/B910970F. PMID 19809738.
  8. ^ Wu Feng and Deng Nansheng (2000): "Photochemistry of hydrolytic iron (III) species and photoinduced degradation of organic compounds: A minireview". Chemosphere, volume 41, issue 8, pages 1137–1147. doi:10.1016/S0045-6535(00)00024-2
  9. ^ Rellán-Álvarez R, Giner-Martínez-Sierra J, Orduna J, Orera I, Rodríguez-Castrillón JÁ, García-Alonso JI, et al. (2010). "Identification of a Tri-Iron(III), Tri-Citrate Complex in the Xylem Sap of Iron-Deficient Tomato Resupplied with Iron: New Insights into Plant Iron Long-Distance Transport". Plant and Cell Physiology. 51 (1): 91–102. doi:10.1093/pcp/pcp170. PMID 19942594.
  10. ^ a b c "Xoanacyl EPAR". European Medicines Agency (EMA). 27 March 2025. Retrieved 29 March 2025. Text was copied from this source which is copyright European Medicines Agency. Reproduction is authorized provided the source is acknowledged.
Allikas: https://en.wikipedia.org/wiki/Ferric_citrate
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