Distribution and Importance of the Plant
The genus Campanula (family Campanulaceae) comprises approximately 300 species distributed across the northern hemisphere, many of these in mountainous areas. The genus generally inhabits meadow and subalpine regions, many species requiring full sun for optimal development. All species are herbaceous, and the name refers to the bell-shaped, blue flowers of the majority of the species. The species are perennials, biannuals, or annuals.
A few species, Campanula glomerata, C. persicifolia, C. rotundifolia, C. bononiensis, C. sibirica, and C. patula have been used locally for preparation of traditional drugs in Russian folk medicine, and, in Italy, similar use has been made of C. medium, C. cervicaria, C. rotundifolia, C. latifolia, and C. trachelium (). Preparations were used to treat epilepsy, nervous diseases, coughs, headache, rheumatism, and inflammation. Many of the medicinal qualities attributed to these species are similar to the use in oriental medicine of drugs made from the closely related Platycodon grandiflorum (a), a species originally classified in the genus Campanula, and from species of the allied genera Adenophora () and Codonopsis (). Commercial cultivation of Campanula is mainly for ornamental purposes, the value of the European production being estimated in the range of 25 million DM per year for pot plants plus a minimum of 4 million DM for cut flowers (Association of Dutch Flower Auctions). Some of the larger species, e.g., G. medium and G. pyramidalis, have traditionally been used as cut flowers, and a number of smaller species, in particular G. carpatica and G. isophylla, are grown as pot plants. On a smaller scale, a wide range of species are used as perennials and by alpine gardening enthusiasts.
The plants used in folk medicine were collected from nature. Drugs were made from roots or from the above-ground parts of flowering plants, that were dried and prepared as broths or infusions. The roots and leaves of one species, C. rapunculoides, can be used as a vegetable. No information is available regarding commercial production of drugs from Campanula. A number of species have been investigated for their contents of metabolites of possible pharmacological importance. In addition, one paper states the isolation of two alkaloids, campedin and (-)lobeline, from C. medium ().
In many of these investigations the plant material consisted of mixtures of plant organs, often all epigeal parts of flowering plants. However, at least the contents of flavonoids, including anthocyanins, and phenolic acid derivatives show dramatic differences when comparing leaves, stems, developing flower buds, and petals. Also for inulins and polyacetylenes, differences were found when more than one plant part was tested. Therefore, some investigations should be considered only as a guideline to the compounds present in all tissues of the plant, since precise information on the relative proportions of flowers, leaves, stems, and flower buds is not available.
Campanula species contain many of the secondary compounds that are the active principles in plants used for medicinal purposes. Generally, the compounds shown in Table 1 or closely related ones are also found in genera of more commonly utilized medicinal plants such as Platycodon, Codonopsis, and Adenophora, (). Campanula is thus a genus with a possible unexploited potential as source of medicinal secondary metabolites, as pointed out by Barnaulov et al. (1983) and Tada et al. (1996). It may be fruitful in a survey among Campanula species to search specifically for additional compounds known to occur in, e.g., Platycodon grandiflorum (). Platycodon grandiflorum is grown on a commercial scale in China for production of the traditional drug Jiejeng, in Japan (Kikyo) and in Korea (Doraji).
Commercial propagation of Campanula for ornamental purposes is by seed, division, or cuttings. Biannual species, such as Campanula medium and C. pyramidalis, are seed-propagated, since the plant usually dies after flowering. In addition to seeds, the perennial species, e.g., C. isophylla and C. carpatica, are propagated by division or cuttings depending on the growth habit of each species.
Although micropropagation of Campanula is relatively easy, it is used only to a small extent, since this propagation method is economically competitive only in special cases, e.g., to propagate disease-free elite stock plants, initial multiplication of new cultivars, or clonal propagation of biannual species.
Campanula (Bellflower) Species: Conclusion and Prospects
Plants of the genus Campanula are used mostly as ornamentals. However, a number of species have been used in folk medicine, and as far as is known the contents of secondary metabolites are similar to species with established medicinal properties from other genera, e.g., Platycodon grandiflorum.
Two kinds of in vitro systems were established for investigations of accumulation of secondary metabolites by growing specific plant organs in isolation. These are flower bud cultures of C. isophylla and C. carpatica for investigations of anthocyanins, and hairy root cultures of C. medium that accumulate polyacetylenes. In both cases, the results have implications for understanding the control of biosynthesis of secondary metabolites, in both tissue culture and the physiology of intact plants. The genus is relatively easy to cultivate in vitro.
Selections from the book: “Medicinal and Aromatic Plants X”, (1998).