Tonic water in the context of Canada Dry

Gentiana (/ˌdʒɛntʃiˈeɪnə/) is a genus of flowering plants belonging to the gentian family (Gentianaceae), the tribe Gentianeae, and the monophyletic subtribe Gentianinae. With over 300 species, it is considered a large genus. Gentians are notable for their mostly large trumpet-shaped flowers, which are often of an intense blue hue, though some are also bright yellow. The type species of the genus is Gentiana lutea.

The genus name is a tribute to Gentius, an Illyrian king who may have discovered tonic properties in gentians.

Quinine is a medication used to treat malaria and babesiosis. This includes the treatment of malaria due to Plasmodium falciparum that is resistant to chloroquine when artesunate is not available. While sometimes used for nocturnal leg cramps, quinine is not recommended for this purpose due to the risk of serious side effects. It can be taken by mouth or intravenously. Malaria resistance to quinine occurs in certain areas of the world. Quinine is also used as an ingredient in tonic water and other beverages to impart a bitter taste.

Common side effects include headache, ringing in the ears, vision issues, and sweating. More severe side effects include deafness, low blood platelets, and an irregular heartbeat. Use can make one more prone to sunburn. While it is unclear if use during pregnancy carries potential for fetal harm, treating malaria during pregnancy with quinine when appropriate is still recommended. Quinine is an alkaloid, a naturally occurring chemical compound. It possesses a C₉H₇N quinoline functional group (pyridine fused to benzene).

A cocktail is a mixed drink, usually alcoholic. Most commonly, a cocktail is a combination of one or more spirits mixed with other ingredients, such as juices, flavored syrups, tonic water, shrubs, and bitters. Cocktails vary widely across regions of the world, and many websites publish both original recipes and their own interpretations of older and more famous cocktails.

Bitterness, also known as bitter, is one of the most sensitive of tastes, and many experience it as unpleasant, sharp, or off-putting, but it is sometimes desirable and intentionally added via various bittering agents. Common bitter foods and drinks include coffee, unsweetened cocoa, South American mate, coca tea, Momordica charantia, unripe olives, citrus peel, some varieties of cheese, many plants in the Brassicaceae family, Taraxacum greens, Marrubium vulgare, wild chicory, and escarole. The ethanol in alcoholic beverages tastes bitter, as do the additional bittering ingredients found in some alcoholic beverages, including hops in beer and gentian in bitters. Quinine is also known for its bitter taste and is found in tonic water.

Bitterness is of interest to those studying evolution, as well as to various health researchers as a large number of naturally occurring bitter compounds are known to be toxic. The ability to detect bitter-tasting, toxic compounds at low thresholds is thought to serve an important protective function. Plant leaves often contain toxic compounds, and among leaf-eating primates there is a tendency to prefer immature leaves, which tend to be higher in protein and lower in fiber and toxins than mature leaves. Among humans, various food processing techniques are used worldwide to detoxify otherwise inedible foods and make them palatable. Furthermore, the use of fire, changes in diet, and avoidance of toxins have led to neutral evolution in human bitterness sensitivity. This has allowed for several loss-of-function mutations that have resulted in a reduced sensory capacity for bitterness in humans compared to other species.