Ruta graveolens (Rutaceae) and its tissue cultures are investigated from a wide variety of aspects, such as botanical studies, medicinal activities, chemical constituents and biosynthesis of some compounds. The in vitro culture of Ruta, quick-growing and with strong biogenetic potentialities, is an optimal implement for biochemical and physiological studies, and many research teams are using it in various fields which are reported in this chapter.
Distribution and Importance of the Plant
The genus Ruta belongs to the family Rutaceae, subfamily Rutoideae and tribe Ruteae. The subtribe Rutinae contains the following genera: Ruta L., Haplophyllum A. Juss., Thamnosma Torr. and Fr. and Boenninghausenia Reichb. Engler (1931) included Ruta and Haplophyllum in one genus. However, Waterman (1975) found that from a chemical standpoint Haplophyllum and Thamnosma are similar, but quite different from Ruta.
According to the Flora Europaea, five species are assigned to the genus Ruta (). Ruta graveolens L. (common names: Engl.: common rue, herb of grace; French: rue fetide; German: Gartenraute; Spanish: ruda, arruda) is a well-known evergreen, half shrubby plant of 0.5 to 1 m in height, with leaves two- to three-pinnate and glaucous. The flowers, small and yellow, are distributed in cymes with a terminal pentamerous flower and some tetramerous flowers. The fruits are follicles with black seeds. The whole plant has a strong, heavy, unpleasant smell and a bitter, acrid pungent taste owing to its volatile oil. R. graveolens originated in meridional Europe and grows in the Balkan peninsula, the Crimea, and perhaps elsewhere in the Mediterranean region. This species was widely naturalized in South and South-central Europe and was introduced into numerous countries, including North America and southwestern Asia, for ornamental and medicinal purposes. R. graveolens has been divided by some authors into R. hortensis Mill, and R. divaricata Tenore, which differed in colour and in flavour, but Flora Europeae does not support this division. A horticultural variety with white-edged leaves (van variegata) is sometimes available.
R. graveolens was famous in ancient Roman times, the Middle Ages and the Renaissance. The plant and its oil (obtained by distillation of the inflorescences) are still used, and their pharmaceutic applications, antimetrorrhagic, antispasmodic and anthelminthic effects appear to be proved. The antispasmodic effects are linked to various alkaloids and coumarins. Indeed, some of the isolated substances, such as rutamarin, arborinine, gravelliferone methyl ether and rutarin showed antispasmodic activity which in their affinity, kinetics of action and duration of effect were comparable to well-known antispasmodic drugs such as papaverine. Antibiotic and bacteriostatic products belonging to the coumarin group (umbelliferone, psoralen) have been isolated from the leaves. In homoeopathia at present some patent medicines, used as revulsive, are available. (Ruta graveolens is used alone or associated with Tamus communis) (). R. graveolens is recorded as a medicinal plant in some official and traditional Pharmacopaea (French, Tunisian, Chinese, etc.). For example, in China this species is used for treating febrile disease, flu, rheumatism, infantile convulsion, dysuresia, diarrhoea, hernia, amenorrhoea, traumatic injury, suppurative infection of the skin, snake bites, miasma, epistaxis, toothache and furuncle.
Besides pharmaceutical applications, Ruta graveolens is used in food and cosmetics. Leaves, pickled fruits and ripe fruits have been used as condiments. The plant and its oil are registered (No. 412) as a natural aromatic product authorized by the European Council. The dosage of methylnonylcetone (2-undecanone) is accepted under 5 ppm in the final product. The use of Ruta oil and of the benzenic extracts of the inflorescence is limited.
In fact, this species and its oil show some toxicity for mankind. Consumption of 2.5 g to 5 g of this plant at one time may result in toxic symptoms.
The abortive effects, known since antiquity, might be due to really ocytocical properties,, but the abortion is the result of toxic doses. The volatile oil also causes hepatonephritis in rabbit and guinea pig, it has a severe incidence of bowels and uterus inducing abortions, convulsions and haemorrhaging. It is phototoxical, bacteriostatical and anthelminthical. The LD50 is 2.54 g/kg for the leaf oil and 3.73 g/kg for the fruit oil in experiments on mice.
Ruta graveolens: Conclusions
Many authors have realized the interest of Ruta graveolens tissue cultures due to a very satisfying growth in vitro, an autotrophic aptitude towards phytohormones and also towards light and especially very strong biogenetic potentialities. These very abilities which lead to varying results can then be pointed out:
- - The localization of accumulation sites of essential oils, as well as of some alkaloids in in vitro tissues.
- - The biogenesis mechanism of alkaloids and coumarins, while some intermediate compounds have not yet been isolated.
- - The relation between differentiation of tissues and metabolite production.
- - The enhancement of metabolite production by using fungal elicitors.
- - The availability of new molecules which are not found in the whole plant.
All these cultures of rue could lead to a wide field of physiological applications.
Selections from the book: “Medicinal and Aromatic Plants II”, 1989.