September 18, 2017
I first fought malaria; now on to Zika.
What molecule am I?
Image of Hydroxychloroquine 3D Image of Hydroxychloroquine

Hydroxychloroquine is a drug that was used originally to treat malaria, especially in patients who could not tolerate the similar compound chloroquine. It also has been used to combat autoimmune diseases such as lupus erythematosus.

In 1950, chemists Alexander R. Surrey and Henry F. Hammer at the Sterling–Winthrop Research Institute (Rensselaer, NY) published a synthesis of hydroxychloroquine. The parent company, Sterling Drug, obtained a US patent on the compound and its method of preparation the same year.

Fast-forward to the era of the Zika virus: Observing that the virus does not affect pregnant mice engineered to suppress a key autophagy* gene, Indira U. Mysorekar and colleagues at the Washington University School of Medicine (St. Louis) treated normal Zika-infected mice with autophagy-inhibiting hydroxychloroquine. The treated mice had less placental and fetal damage than the control group. The researchers postulate that the drug prevents Zika from crossing the placental barrier.

*Autophagy is the mechanism by which the body destroys damaged cellular material. The Zika virus overexpresses autophagy in the placenta.

MOTW Updates: September 18, 2017

Chlorpyrifos, a controversial thiophosphate insecticide, was the Molecule of the Week for November 8, 2010. In May of this year, its manufacturers pressured the US Environmental Protection Agency to rescind damaging biological evaluations of the pesticide. The controversy has now been exacerbated by EPA’s decision to delay any decision to ban chlorpyrifos until 2022.

Adenosine, the Molecule of the Week for July 5, 2010, is the root structure of the energy-tranfer coenzymes ATP and ADP. More recently, it has been used as a component of antiwrinkle skin creams. The Teresian Carmelites, a charitable religious group, first marketed adenosine-containing Easeamine products in 2009. Shortly thereafter, however, cosmetic giant L’Oréal began to sell similar products. The Teresians have sued L’Oréal for violating the patents that they licensed from the University of Massachusetts.

fast facts

CAS Reg. No. 118-42-3
Molar mass 335.87 g/mol
Formula C18H26ClN3O
Appearance White crystals 
Melting point 90 ºC 
Water solubility 26 mg/L

MOTW update: 
April 20, 2020

Hydroxychloroquine was originally developed as a malaria drug, in 2017 it was being explored as a treatment for patients suffering from the Zika virus.* During the current coronavirus pandemic, dozens of clinical trials are under way to evaluate its efficacy against the SARS-CoV-2 virus.

*The US Food and Drug Administration has not approved hydroxychloroquine as a vaccine or treatment for Zika virus.

Chemical Abstract Service - a division of ACS

Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

Molecule of the Week needs your suggestions!

If your favorite molecule is not in our archive, please send an email to motw@acs.org. The molecule can be notable for its current or historical importance or for any quirky reason. Thank you!

Stay Ahead of the Chemistry Curve

Learn how ACS can help you stay ahead in the world of chemistry.