Quinine

C 20
H 24
N 2
O 2

Ball-and-stick Stick Space-filling

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48 atoms, 51 bonds.

IUPAC name: (R)-[(2S,4S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol
Molar mass: 324.424(49) g/mol
Atoms: 48
SMILES: COC1=CC2=C(C=CN=C2C=C1)C(C3CC4CCN3CC4C=C)O
InChIKey: LOUPRKONTZGTKE-WZBLMQSHSA-N
PubChem CID: 3034034

Made of

C H N O

Structural formula of quinine. Each unlabelled corner is a carbon atom, and the 18 hydrogens on carbon are not drawn. Wedges come toward you, hashes go back. It shows which atoms are joined to which, not the shape. The model above shows the shape.

Quinine takes its name from kina, the Quechua word for bark, according to Emerging Infectious Diseases, the journal of the US Centers for Disease Control and Prevention (CDC). HSDB, the Hazardous Substances Data Bank, lists it as the chief alkaloid of cinchona bark, the main nitrogen-containing base the bark yields. It tastes very bitter. ChEBI (Chemical Entities of Biological Interest) files it as cinchonidine with a methoxy group, OCH₃, in place of the hydrogen at position 6 of the quinoline ring.

PubChem names it (R)-[(2S,4S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol. The chemical inventories of Australia and New Zealand list it under another name, Cinchonan-9-ol, 6′-methoxy-, (8α,9R)-. That name gives the carbon holding the hydroxyl the number 9 and the methoxy position 6′. Quinine shows a blue fluorescence, especially bright in dilute sulfuric acid, and in alcohol it turns polarised light to the left (HSDB).

Structure and bonding

Quinine joins two unlike halves through one carbon carrying an O–H group. One half is quinoline, two fused six-membered rings of nine carbons and one nitrogen, bearing the methoxy group. The other is a cage of seven carbons and one nitrogen, the quinuclidine ring system. Three two-carbon bridges run from its nitrogen to a far carbon, and a CH=CH₂ group hangs off the cage.

In Ball-and-stick, the two quinoline rings carry four C=C bonds and one C=N between single bonds. Such alternation is a conjugated system, whose pi bonds (each double bond’s second bond) are spread over the whole stretch on Chem1’s account; benzene sets out the idea. Seen edge-on, the quinoline rings, the methoxy group’s oxygen and carbon, and the linking carbon lie in one plane.

Labels separate the two nitrogens: one in the ring’s C=N, the other at the cage’s end, with three single bonds and no hydrogen. In the model those bonds form a pyramid, with C–N–C angles of 107.7 to 110.9°. The drawn form is the neutral parent molecule; ChEBI also lists the cation quinine(1+), and the medicine is the salt quinine sulfate.

Where it turns up

The genus Cinchona, in the family Rubiaceae, holds 23 tree species, according to a 2026 review in Emerging Infectious Diseases. They are South American trees about 15 metres tall, bitter in bark, branches and leaves alike, and one appears on Peru’s national coat of arms. Heavy exploitation after the bark proved itself against malaria left the trees highly vulnerable, the review’s author writes. Quinine is made by extraction from the bark, HSDB records.

US food rules quoted in HSDB allow quinine, as its hydrochloride or sulfate salt, as a flavour in carbonated drinks, and the label must declare its presence prominently. MeSH (Medical Subject Headings) records its past use as a bitter flavouring and in common cold preparations, and HSDB lists a veterinary use.

Why it matters

Jesuit missionaries living in Peru came to know the healing bark of “fever trees” in the 1620s, by CDC’s account. MeSH dates the bark’s use to before 1633, and HSDB begins its history in Peru in the middle of the seventeenth century. Carl Linnaeus classified the genus in 1742, by the review’s account. Pierre-Joseph Pelletier and Joseph Bienaimé Caventou isolated two alkaloids from the bark in 1820, naming one of them quinine.

HSDB calls quinine the first known antimalarial and the model for many later drugs against Plasmodium, the malaria parasite. How it acts on the parasite is not well understood, MeSH notes. In test-tube work described in the review, quinine inhibited haem polymerase, an enzyme extracted from Plasmodium falciparum. The review’s author writes that the drug disrupts the parasite’s means of detoxifying itself. The liver breaks quinine down mainly through the enzyme CYP3A4, and the main product, 3-hydroxyquinine, is less active (HSDB).

Properties

Properties of quinine Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 3034034.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₂₀H₂₄N₂O₂
Molar mass	324.424(49) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	20
Hydrogen atoms	24
Nitrogen atoms	2
Oxygen atoms	2
Bonds	51
Single bonds	45
Double bonds	6
PubChem molecular weight	324.4 g/mol	g/mol	PubChem

Safety

Between 1969 and 2006, the US Food and Drug Administration (FDA) received 665 reports of adverse events tied to quinine sulfate, 93 of them deaths. Meanwhile, unapproved versions were sold for leg cramps. FDA acted to remove those products and approved quinine sulfate with a boxed warning on the life-threatening danger of its use for nocturnal leg cramps. The PubChem Laboratory Chemical Safety Summary adds that it may cause an allergic skin reaction, and allergy or asthma symptoms if inhaled.

Questions

What do the parts of quinine's chemical name mean?

Each part names a piece of the 3D model. 6-Methoxyquinolin-4-yl is the flat pair of rings, carrying the methoxy group at position 6 and joined at position 4. 1-Azabicyclo[2.2.2]octan-2-yl is the cage, with nitrogen at position 1 and three two-carbon bridges. 5-Ethenyl is the CH=CH₂ group on the cage, and methanol is the O–H carbon linking the halves. The R and S letters fix the arrangement in space at four carbons.

Is quinine still used to treat malaria?

Yes, within limits. In the United States, quinine sulfate is a prescription medicine, sold as Qualaquin and approved only for uncomplicated malaria caused by Plasmodium falciparum; it has proved effective in regions where that parasite resists chloroquine. FDA has not approved it for severe or complicated malaria. The World Health Organization's Model List of Essential Medicines includes it as a curative antimalarial for Plasmodium falciparum malaria.

Is quinine an acid or a base?

A base. ChEBI lists it as the conjugate base of quinine(1+), the cation it becomes on gaining a proton, and HSDB records a pH of 8.8 for a saturated solution in water. Quinine dissolves in acids by forming salts, and salts are common forms in use: the US medicine is quinine sulfate, while US food rules name the hydrochloride and the sulfate. HSDB also lists quinine trihydrate, which holds water in its crystals.

Why did the FDA act against quinine for leg cramps?

Unapproved quinine sulfate products had been marketed to relieve leg cramps, and many of their labels lacked the approved drug's warning of life-threatening dangers. A 1994 FDA rule found no evidence that quinine works for nocturnal leg cramps and judged its risks, unpredictable life-threatening reactions needing hospital care among them, to outweigh any benefit for a benign condition that passes by itself. Reports to FDA named heart rhythm disturbances, kidney failure and myasthenia gravis, a neurological disorder, among the harms.

Made of the same elements

C₁₇H₂₁NO Diphenhydramine 40 atoms, 41 bonds.
C₁₄H₂₂N₂O Lidocaine 39 atoms, 39 bonds.
C₁₃H₂₁NO₃ Albuterol 38 atoms, 38 bonds.
C₁₄H₁₈N₂O₅ Aspartame 39 atoms, 39 bonds.
C₁₃H₁₆N₂O₂ Melatonin 33 atoms, 34 bonds.
C₁₂H₁₇NO DEET 31 atoms, 31 bonds.
C₁₁H₁₂N₂O₂ Tryptophan 27 atoms, 28 bonds.
C₁₀H₁₂N₂O Serotonin 25 atoms, 26 bonds.

All 25 compounds made of carbon, hydrogen, nitrogen and oxygen

C₉H₁₃NO₃ Epinephrine 26 atoms, 26 bonds.
C₉H₁₁NO₂ Phenylalanine 23 atoms, 23 bonds.
C₈H₁₁NO₂ Dopamine 22 atoms, 22 bonds.
C₆H₁₃NO₂ Isoleucine 22 atoms, 21 bonds.
C₆H₁₃NO₂ Leucine 22 atoms, 21 bonds.
C₉H₁₁NO₃ Tyrosine 24 atoms, 24 bonds.
C₈H₉NO₂ Acetaminophen 20 atoms, 20 bonds.
C₈H₁₀N₄O₂ Caffeine 24 atoms, 25 bonds.
C₅H₉NO₄ Glutamic acid 19 atoms, 18 bonds.
C₅H₆N₂O₂ Thymine 15 atoms, 15 bonds.
C₃H₇NO₂ Alanine 13 atoms, 12 bonds.
C₄H₄N₂O₂ Uracil 12 atoms, 12 bonds.
C₄H₅N₃O Cytosine 13 atoms, 13 bonds.
C₂H₅NO₂ Glycine 10 atoms, 9 bonds.
C₅H₅N₅O Guanine 16 atoms, 17 bonds.
C₅H₄N₄O₃ Uric acid 16 atoms, 17 bonds.
CO(NH₂)₂ Urea 8 atoms, 7 bonds.