Ruta graveolens

Ruta graveolens [L. "strong smelling rue"], commonly known as rue, common rue or herb-of-grace, is a species of "Ruta" grown as an ornamental plant and herb. It is native to the Balkan Peninsula. It is now grown throughout the world in gardens, especially for its bluish leaves, and sometimes for its tolerance of hot and dry soil conditions. It is also cultivated as a medicinal herb, as a condiment, and to a lesser extent as an insect repellent.
Etymology.
The specific epithet "graveolens" refers to the strong-smelling leaves.
Uses.
Traditional use.
In the ancient Roman world, the naturalists Pedanius Dioscorides and Pliny the Elder recommended that rue be combined with the poisonous shrub oleander to be drunk as an antidote to poisonous snake bites.
The "Tacuinum Sanitatis", a medieval handbook on wellness, lists these properties of rue:
Culinary use.
Rue has a culinary use, but since it is bitter and gastric discomfort may be experienced by some individuals, it is used sparingly. Although used more extensively in former times, it is not a herb that is typically found in modern cuisine. Today it is largely unknown to the general public and most chefs, and unavailable in grocery stores. It is a component of berbere, the characteristic Ethiopian spice mixture, and as such is encountered in Ethiopian cuisine. Also in Ethiopia, fresh rue is dipped in coffee before drinking it. See e.g. Ruta in Coffee in Ethiopia
It has a variety of other culinary uses:
Other.
Rue is also grown as an ornamental plant, both as a low hedge and so the leaves can be used in nosegays.
Most cats dislike the smell of it, and it can, therefore, be used as a deterrent to them (see also "Plectranthus caninus").
Caterpillars of some subspecies of the butterfly "Papilio machaon" feed on rue, as well as other plants. The caterpillars of "Papilio xuthus" also feed readily on it.
In South India, rue is recommended for home gardens to repel snakes (however the effectiveness is unknown).
Rue is also a common ingredient in witchcraft and spell making. During the Middle Ages it was a symbol of recognition between witches. The Catholic Church also used a branch of rue to sprinkle holy water on its followers: during this time it was known as the "herb of grace." Hasidic Jews also were taught that rue should be placed into amulets to protect them from epidemics and plagues. This was taught by Rabbi Isaac of Komarno in his comments to "Sefer Adam Yashar" in the name of Rabbi Isaac Luria.
In North West frontier province of Pakistan and in Afghanistan is still a part of daily life. In song Rue (Spelanai) refer to welcome and burn seeds for bad wibes , Insects and room cleanser it's always been used .
Toxicity.
Rue extracts are mutagenic and hepatotoxic. Large doses can cause violent gastric pain, vomiting, systemic complications, and death.
Exposure to common rue, or herbal preparations derived from it, can cause severe phytophotodermatitis which results in burn-like blisters on the skin.
Chemistry.
A series of furanoacridones and two acridone alkaloids (arborinine and evoxanthine) have been isolated from "R. graveolens". It also contains coumarins and limonoids.
Cell cultures produce the coumarins umbelliferone, scopoletin, psoralen, xanthotoxin, isopimpinellin, rutamarin and rutacultin, and the alkaloids skimmianine, kokusaginine, 6-methoxydictamnine and edulinine.
The ethyl acetate extract of "R. graveolens" leaves yields two furanocoumarins, one quinoline alkaloid and four quinolone alkaloids.
The chloroform extracts of the root, stem and leaf shows the isolation of the furanocoumarin chalepensin.
The essential oil of "R. graveolens" contains two main constituents, undecan-2-one (46.8%) and nonan-2-one (18.8%).
Symbolism.
The bitter taste of its leaves led to rue being associated with the (etymologically unrelated) verb "rue" "to regret". Rue is well known for its symbolic meaning of regret and it has sometimes been called "herb-of-grace" in literary works. In mythology, the basilisk, whose breath could cause plants to wilt and stones to crack, had no effect on rue. Weasels who were bitten by the basilisk would retreat and eat rue in order to recover and return to fight.
In the Bible.
Rue is mentioned in the Bible, Luke 11:42: "But woe unto you, Pharisees! For ye tithe mint and rue and all manner of herbs".
In Lithuania.
Rue is considered a national herb of Lithuania and it is the most frequently referenced herb in Lithuanian folk songs, as an attribute of young girls, associated with virginity and maidenhood. It was common in traditional Lithuanian weddings for only virgins to wear a rue () at their wedding, a symbol to show their purity. 
In Ukraine.
Likewise, rue is prominent in Ukrainian folklore, songs and culture. In the Ukrainian folk song "Oi poli ruta, ruta" (O, rue, rue in the field), the girl regrets losing her virginity, reproaching the lover for "breaking the green hazel tree". "Chervona Ruta" (Червона Рута—"Red Rue") is a song, written by Volodymyr Ivasyuk, a popular Ukrainian poet and composer. Pop singer Sofia Rotaru performed the song in 1971.
In Jewish culture.
"Una Matica de Ruda" is a traditional Sephardic wedding song.
In English literature.
It is one of the flowers distributed by the mad Ophelia in William Shakespeare's "Hamlet" (IV.5):
It was planted by the gardener in "Richard II" to mark the spot where the Queen wept upon hearing news of Richard's capture (III.4.104–105):
It is also given by the rusticated Perdita to her disguised royal father-in-law on the occasion of a sheep-shearing (Winter's Tale, IV.4):
It is used by Michael in Milton's "Paradise Lost" to give Adam clear sight (11.414): 
Rue is used by Gulliver in "Gulliver's Travels" (by Jonathan Swift) when he returns to England after living among the "Houyhnhnms". Gulliver can no longer stand the smell of the English Yahoos (people), so he stuffs rue or tobacco in his nose to block out the smell. "I was at last bold enough to walk the street in his (Don Pedro's) company, but kept my nose well with rue, or sometimes with tobacco".