Рута

Rue, Ruta graveolens, belongs to the family Rutaceae. It is a woody, perennial shrub native to the Mediterranean. Its leaves are oblong, blue green and arranged bipinnately with rounded leaflets. The specific epithet graveolens refers to the strong-smelling leaves.

Gardens throughout the world hold it, mostly for its bluish leaves and sometimes because it tolerates hot, dry soil. It is also cultivated as a culinary herb, and to a lesser extent as an insect repellent and incense.

Origin and Production

In leaves of R. graveolens, wild-grown and micropropagated samples gave almost the same oil yield, 0.80% and 0.84% respectively. Oil yields and chemical profiles of Ruta species vary considerably between cultivated and wild-growing plant material. In Ruta oils the two main ketones, 2-undecanone and 2-nonanone, vary considerably in amount, mainly with climate, soil quality, geographical source, collection time and processing methods.

Chemistry

The essential oil of R. graveolens has two main constituents, undecan-2-one at 46.8% and nonan-2-one at 18.8%. Essential oils of the genus Ruta predominantly contain aliphatic ketones such as 2-undecanone and 2-nonanone, and lack any significant amounts of terpenes. 2-Undecanone, also called methyl nonyl ketone, is a colorless oil with the formula CH₃C(O)C₉H₁₉. 2-Undecanone is usually produced synthetically but can also be extracted from plant sources, including the essential oil of rue. Rue also contains limonoids. A leaf extract of R. graveolens yields two furanocoumarins, one quinoline alkaloid and four quinolone alkaloids.

Phototoxicity and Toxicity

Rue can cause photodermatitis of skin exposed to ultraviolet light. Exposure to common rue, or to herbal preparations derived from it, can cause severe phytophotodermatitis, with burn-like blisters on the skin. Rue oil is known to contain psoralens. Rue extracts are mutagenic and hepatotoxic, and large doses can cause potentially fatal liver injury. Pregnant women should strictly avoid it, since it is an abortifacient and teratogen.

Culinary Use

Because rue is bitter and may cause gastric discomfort in some individuals, it is used sparingly in cooking. Rue is used as a traditional flavouring in Greece and other Mediterranean countries. In Istria and in northern Italy it gives a special flavour to grappa, and a little branch of the plant is usually found in the bottle.

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