The herb Ruta graveolens, commonly known as rue, is a perennial plant native to the Mediterranean region. This strongly aromatic shrub, which belongs to the citrus family (Rutaceae), has been cultivated for centuries for its distinctive blue-green foliage and pungent, slightly bitter scent. Throughout history, the plant’s potency has been recognized, leading to its dual reputation as both a highly valued medicinal and spiritual herb and a potential toxin. Its name, graveolens, hints at its strong odor, which signals the need for careful consideration when handling or consuming the plant.
Historical and Traditional Applications
Historically, rue was widely incorporated into folk medicine across various cultures. Ancient Greek and Roman physicians, including Pedanius Dioscorides and Pliny the Elder, recommended rue for treating a multitude of ailments, from digestive complaints to nervous system disorders. The herb was often employed as an antispasmodic to relieve muscle cramps and was a traditional remedy for conditions like fever and toothache. Rue has also been traditionally used as an emmenagogue to stimulate menstrual flow.
Beyond physical remedies, rue held significant symbolic importance, often referred to as the “herb-of-grace” in medieval times. In many traditions, it was used to ward off negative influences or pests, with sprigs hung in homes or scattered to repel insects. Its historical use in cooking was as a bitter flavoring agent, used sparingly in dishes like eggs, cheese, or to flavor the Italian alcoholic beverage grappa alla ruta. Due to its intense flavor and known toxicity, its culinary use is now minimal and largely limited to specific regional traditions.
Chemical Components and Modern Research
The strong biological activity of rue is directly linked to its complex profile of active phytochemicals. These compounds include alkaloids, flavonoids, and volatile oils. Prominent among the alkaloids are acridone and quinoline derivatives, while the flavonoids include rutin and quercetin, which have been studied for their antioxidant effects. The essential oil produced by rue is notably high in long-chain ketones, such as 2-undecanone and 2-nonanone, which are largely responsible for the plant’s unique, pungent aroma.
A particularly significant group of compounds are the furocoumarins, which include psoralen and methoxypsoralen. These substances are central to the herb’s phototoxic nature and are the focus of modern pharmacological research. Scientific investigations have explored rue’s potential for anti-inflammatory, antimicrobial, and insecticidal properties. Other studies are examining its effects on bitter taste receptors and its potential anti-cancer activity, demonstrating a continued scientific interest in this complex plant.
Safety Concerns and Handling Rue
Despite its rich history, rue is not a benign herb and must be approached with extreme caution due to its inherent toxicity. A major concern when handling the fresh plant is a condition known as phytophotodermatitis, a severe skin reaction caused by the furocoumarins in the sap. When the skin comes into contact with the plant’s oils and is subsequently exposed to ultraviolet light, the compounds become activated, leading to a chemical burn that can result in redness, blistering, and hyperpigmentation.
Ingesting rue, especially in large amounts or in concentrated forms like essential oil, poses a risk of severe internal toxicity. Consumption can lead to violent gastrointestinal upset, vomiting, and more serious systemic complications, including potential damage to the liver and kidneys. Case reports of multiorgan toxicity and even death following the consumption of rue decoctions underscore the plant’s danger. For this reason, the use of rue is considered obsolete by many modern herbalists.
Rue is strictly contraindicated for pregnant women because of its potent abortifacient and teratogenic properties, historically used to terminate pregnancies. The compounds within the herb can be toxic to the developing embryo or fetus. Therefore, individuals should always wear gloves and long sleeves when pruning or harvesting the fresh plant to prevent contact dermatitis and should avoid sun exposure on any skin that may have touched the sap.