Quinazolinone is a heterocyclic chemical compound. There are two structural isomer

Isomer

In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...

s, 2-quinazolinone and 4-quinazolinone, with the 4-isomer being the more common.

Derivatives

Quinazolinones are also a class of drugs which function as hypnotic

Hypnotic

Hypnotic drugs are a class of psychoactives whose primary function is to induce sleep and to be used in the treatment of insomnia and in surgical anesthesia...

/sedative

Sedative

A sedative or tranquilizer is a substance that induces sedation by reducing irritability or excitement....

s that contain a 4-quiazolinone core. Their use has also been proposed in the treatment of cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

. Examples include afloqualone

Afloqualone

Afloqualone is an analogue of methaqualone developed in the 1980s in Japan. It has sedative and muscle relaxant effects, and has had some clinical use, although it causes photosensitization as a side effect which can cause skin problems such as dermatitis.- See also :* Methaqualone* Diproqualone*...

, cloroqualone

Cloroqualone

Cloroqualone is an analogue of methaqualone developed in the 1980s and marketed mainly in France and some other European countries. It has sedative and antitussive properties, and was sold either alone or in combination with other ingredients as a cough medicine...

, and diproqualone

Diproqualone

Diproqualone is an analogue of methaqualone developed in the 1980s and marketed mainly in France and some other European countries. It has sedative, anxiolytic, antihistamine and analgesic properties, and is used primarily for the treatment of inflammatory pain associated with osteoarthritis and...

.
Alkaloid

Alkaloid

Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...

s containing the quinzolinone core include febrifugine

Febrifugine

Febrifugine is a quinazolinone alkaloid first isolated from Chinese herb Dichroa febrifuga, but also found in the garden plant Hydrangea....

 and halofuginone

Halofuginone

Halofuginone is a coccidiostat used in veterinary medicine. It is a synthetic halogenated derivative of febrifugine, a natural quinazolinone alkaloid which can be found in the Chinese herb Dichroa febrifuga . Collgard Biopharmaceuticals is developing halofuginone for the treatment of scleroderma...

.