Centaurium erythraea
Distribution and Importance
Centaurium erythraea Rafn (Synonym: C. umbellatum Gilib., C. minus Moench, Erythraea centaurium Pers., Commonly Centaury), is a medicinal plant known for centuries; it was described by Dioscorides as early as in the first century A. D. For medicinal purposes its aerial flowering part, mostly called Centaurii herba or Herba centaurii minoris is used. According to some pharmocopoeias, this drug may include also C pulchellum (Sw.) Druce, C uliginosum (W. et K.) Beck (Synonym: C. littorale ssp. uliginosum (W. et K.) Melderis) and C. majus (Hoffm. et Link) Zeltner (Synonym: Erythraea major Hoffm. et Link).
Centaurium erythraea () is a member of the family Gentianaceae. It is a herbaceous winter-annual plant, 2-50 cm high, with a basal rosette of leaves and usually solitary, but sometimes several erect stems branched at the top. Basal leaves are obovate or elliptic (10-50×8-20 mm), prominently three to seven-veined. Cauline leaves are shorter, narrow, and acute, but never parallel-sided. Flowers are sesile or subsesile, pink, often clustered, forming a dense corymb-like cyme.
Centaurium erythraea is distributed in oceanic Europe and the Mediterranean. Formerly, Centaurii herba was mainly collected from local wild populations throughout Europe; today it is collected mostly from wild populations in the Mediterranean region, mainly in Yugoslavia, Algeria, and Morocco.
The crude drug is utilized for preparing tinctures, liquid extracts, syrups, wines, and powders. Since its medicinal application makes mostly use of its high content of bitter substances, it is part of many well-known preparations, such as Tinctura amara, Species amarae, and Vinum amarum to name a few. The pure extract of the drug is known under the name Extractum centaurii minoris and is applied in the treatment of the diseases of the gastrointestinal tract, eczema, wounds, as well as for a sedative, antihelminthic etc. The comprehensive account of its pharmacology was published by Van der Sluis. Further, the drug is used for preparing commercial beverages by some companies (Jan Becher, F. Cinzano, Martini and Rossi).
Demand in the World Market and Conventional Methods for Propagation
The current annual demand for Centaurii herba is, for example, 12000 kg in Czechoslovakia (Suk, pers. commun.), 2000 kg in the Netherlands, and 16000 kg in France (Van der Sluis 1985). This drug had been commonly used until the first half of the century, but recently its consumption has decreased considerably. In the last decade, its consumption for example in Czechoslovakia decreased from 20000 to 12000 kg annually. It has even disappeared altogether from some pharmacopoeias and been replaced by other bitter substances, owing mainly to the decreasing availability of this plant from wild populations. This is in turn due to its collection for medicinal purposes and to the deterioration of its natural habitats. The populations of this winter-annual plant are greatly endangered by collecting, unless at least one quarter of the population is left untouched to ensure reproduction (Stary, pers. commun.). C. erythraea appears in many red lists of endangered plants.
The unavailability of Centaurium erythraea is further due to its following properties, which make its cultivation difficult: (1) unpredictable germination of its seeds, (2) the inability of the plant to grow in dense stands, (3) its inability to compete with common weeds. In addition, the harvesting has to be done carefully so as not to damage the rosette population. Therefore its cultivation is labor-intensive and expensive; moreover, the unpredictable germination makes its results difficult to guarantee.
Secondary Products in Intact Plants
All species of the genus Centaurium synthesize a similar spectrum of secondary products. In this chapter, only secondary products of C. erythraea are reviewed. A detailed study of the secondary products of the genus (together with its chemotaxonomic analysis) was published by Van der Sluis. This section is based mainly on his data.
The main group of secondary products are bitter secoiridoid glucosides, which are very important from the medicinal point of view. Their major constituents are swerosid-type secoiridoid glucosides (swertiamarin, gentiopicroside, sweroside). In addition, the plants contain esters of these secoiridoid glucosides (centapicrin, desacetylcentapicrin), which are accumulated mainly in capsules. The esters are much more bitter than free glucosides (by a factor of several thousands). Highly bitter ester amarogentin, often reported from C. erythraea (), has not been confirmed by the detailed study of Van der Sluis and Labadie. The content of these compounds varies slightly in different populations of this species. This might be correlated with two different ploidy levels reported from this species.
Further, some authors (e.g., Rulko and Witkiewicz) published reports of the isolation of alkaloids (mainly gentianine), which are analogs of secoiridoides having nitrogen instead of oxygen in the pyran ring. Their presence may, however, be only an artifact of extraction by ammonia (Van der Sluis).
Xanthones are the second main type of secondary products of Centaurium erythraea; many hydroxy and methoxy derivatives of xanthone have been described).
Moreover, Centaurium erythraea plants contain high amounts of fatty acids; oleanol acid makes up 0.7% of its dry mass, other acids, such as stearin, palmitin, cerotin, linolen, linol, and oleic acid, are present as well (List and Horhammer 1972). The sterol spectrum of C. erythraea was recently studied by Aquino et al..
Medicinal and Aromatic Plants I (1988)
