September 04, 2017
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The famed Japanese chemist Tetsuo Nozoe first isolated the tropolone monoterpenoid hinokitiol from the wood of the Taiwanese ninoki tree (Chamaecyparis taiwanensis) in 1936. Since then, it has been found in other trees of the Cupressaceae family, although not in the Japanese hinoki.

Beginning in the 2000s, researchers recognized that hinokitiol could be of value as a pharmaceutical, notably for inhibiting the bacterium Chlamydia trachomatis. But this year, chemist Martin Burke and colleagues at the University of Illinois at Urbana–Champaign and at several other institutions discovered a more significant medical use for hinokitiol.

Burke’s goal was to overcome irregular iron transport in animals. Insufficiencies of several proteins can lead to iron deficiency in cells (anemia) or the opposite effect, hemochromatosis. Using gene-depleted yeast cultures as surrogates, the researchers screened a library of small biomolecules for signs of iron transport and therefore cell growth. Hinokitiol popped up as the one that restored cell functionality.

Further work by the team established the mechanism by which hinokitiol restores or reduces cell iron. They then switched their study to mammals and found that when rodents that had been engineered to lack “iron proteins” were fed hinokitiol, they regained iron uptake in the gut. In a similar study on zebrafish, the molecule restored hemoglobin production.

A commentary on the work of Burke et al. nicknamed hinokitiol the “Iron Man molecule”. This is fitting (and ironic) because discoverer Nozoe’s first name can translate into English as “iron man”.

Hinokitiol fast facts

CAS Reg. No.499-44-5
Molar mass164.20 g/mol
AppearanceColorless to pale yellow crystals
Melting point52.0–52.5 ºC 
Water solubility1.2 g/L

MOTW update: November 9, 2020

Hinokitiol is a tropolone monoterpenoid that shows promise as a drug that can regulate iron transport in animals. More recently, Inga Wessels and colleagues at RWTH Aachen University (Germany) showed that zinc supplementation may inhibit COVID-19 viral replication and that zinc ionophores such as hinokitiol may play a role in this process. An ionophore is a compound that binds ions and allows them to be transported through hydrophobic media such as cell membranes.

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