ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Investigation of complexation behavior of piroctone olamine salt with Fe(III) ions and influence on antifungal activity

Zhimin Chen, Liqi Xia, Defeng Gao, Jinhua Li, Jing Wang, Jiantong Li, and Kuan Chang

Key Laboratory of Synthetic and Biological Colloids, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, China

E-mail: jiantong.li@cosmoschem.com

Received: 31 July 2025  Accepted: 5 February 2026

Abstract:

Piroctone olamine (PO) is a widely used antifungal agent in cosmetic and dermatological formulations, particularly effective against Malassezia furfur and Cutibacterium acnes. Despite its broad application, the metal complex behavior of PO and its impact on antifungal activity remain unclear. In this study, the complexation behavior of PO was examined with a panel of disparate metal ions. PO-Fe was synthesized and characterized to investigate the coordination chemistry between PO and Fe³⁺ and evaluate the influence of iron complexation on PO’s antifungal efficacy. PO-Fe was prepared at 25 °C via co-precipitation method and authenticated by a 420 nm UV band, 7.08% Fe content determined by ICP-OES, m/z 765.43 detected by MALDI-MS, and a unique XRD signature. Job’s plots established that hydroxypyridinone oxygens mediate a 3:1 PO: Fe³⁺ complex with logβ 11.3, as corroborated by FTIR and XPS. Importantly, the antifungal activity of PO against Malassezia furfur was diminished by 94% upon complexation with Fe³⁺, suggesting that extracellular iron complex impairs PO’s ability to disrupt intracellular iron homeostasis. These findings provide new insights into the structure–activity relationship of PO and highlight the importance of metal ion interactions in the formulation and performance of antifungal agents.

Graphical abstract

Piroctone olamine (PO) forms a well-defined metal complex (PO-Fe) with Fe³⁺ in a 3:1 stoichiometry, wherein Fe³⁺is coordinated through the oxygen atoms of the hydroxypyridinone ring of PO. Notably, the resulting PO-Fe complex exhibits significantly reduced antifungal activity against Malassezia furfur compared to the free PO.

Keywords: Piroctone olamine; Ferric iron; Complex; Stability constant; Antifungal properties

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04732-6

Chemical Papers 80 (5) 5615–5625 (2026)