Habit and Distribution of the Plant
According to recent studies in plant systematics, the valid name of the medically used camomile is Chamomilla recutita (L.) Rauschert. Linne used the name “Matricaria recutita”, but the plant has become generally known as “Matricaria chamomilla”.
Chamomilla recutita is a member of the family of the Asteraceae. It is an annual herbaceous plant which flowers from May to August and reaches a height of 20-60 cm. It carries leaves with a pinnate structure and inflorescences of 10-20 mm diameter which are located terminally, or in the leaf axils supported by pedicels of 5-10 cm length. The inflorescences (capitula) consist of numerous yellow tubular florets in the center surrounded by a circle of white ligulate florets with all florets imbricated on a hollow inflorescence base. The flowers, and especially the inferior ovaries, are rich in excretory glands containing the valuable essential oil. The fruit is an achene. The original area of distribution was southern and eastern Europe and the Near East. From there the camomile has spread through most of Europe, and today is found from Scandinavia in the north to the Ural mountain range in the east. Its area of distribution has extended further to Iran, Afghanistan, Pakistan, India, China, and Japan on the one hand, and to Egypt, East Africa, and the Congo basin on the other. It was introduced into the Americas (U.S.A., Mexico, Peru, Argentina, Brazil), and Australia, probably together with shipments of grain. In keeping with its modest demands on the prevailing soil conditions (loamy, salty, sandy soils are tolerated) the camomile grows on fallows, dumps, village paths, grasslands, grain fields, and vineyards.
Conventional Practices of Camomile Propagation and Camomile Demand in the World Market
According to the present state of knowledge for therapeutical purposes, a camomile plant type with high contents of (-)-α-bisabolol, cis/trans en-in-dicycloether, matricine, and flavonoids (with a high portion of apigenin-glycosides) is required. The steadily increasing need for high quality drugs cannot be provided by plant collection in the wilderness. For several years the systematic and controlled cultivation of camomile types with reproducible pharmaceutical quality has been promoted worldwide. Today well-bred camomiles are cultivated in Argentina, Bulgaria, Egypt, and Hungary; smaller amounts are grown in Czechoslovakia, Germany, and Spain. They give a drug yield of 500-800 kg per hectare; the drug obtained contains about 1% (dry wt.) essential oil with a high proportion of (-)-α-bisabolol (200-500 mg%) and chamazulene (150-240 mg%).
The annual harvest world-wide is estimated to be 6000-70001 of camomile drug. In the Federal Republic of Germany alone 3000 t of camomile drug are imported annually, representing a value of about $11 million. In 1987 1 kg of high quality camomile oil cost $1700-2300 on the world market.
The various commercial camomile drugs still differ widely as far as the total content of active compounds and the compound spectrum are concerned. This is partly a consequence of the camomile variety cultured. Four or five different chemical types of cultivars are known which are each characterized by the predominance of a different compound of the essential oil spectrum, e.g., bisabolol type, bisabolonoxide type, bisabololoxide A type, bisabololoxide B type. On the other hand, the compound content and pattern of the drug are influenced by daylength, culture and fertilization methods, seasonal weather fluctuation, and the developmental state of the flower heads at harvest time. In the coming years progress in camomile breeding and improvements in culture methods should result in a supply with more standardized camomile drugs. Breeding programs to increase homogeneously all groups of medically important compounds, especially the apigenin-glycoside content, need to be designed. Since the demand for camomile drugs of high quality is expected to increase in the future, additional efforts concerning breeding programs should repay on a long-term basis.
Conclusions and Prospects
The few papers concerned with the secondary compound production by cell cultures of Chamomilla recutita have yielded very interesting results with respect to the formation and accumulation of volatile compounds and with respect to techniques for manipulating such formation. Up to the present it has, however, proved impossible to establish a callus or suspension culture which continuously produces or releases high yields of terpenes of therapeutical importance, e.g., matricine and (—)-α-bisabolol. In plants the accumulation of these compounds is restricted to the flower heads and consequently underlies tissue-specific regulations, the mechanisms of which are barely understood. At the same time many experiments have shown that cell cultures of camomile do not synthesize flavonoids, the other class of compounds of therapeutical importance. At the present, no indication is thus available which points to a forthcoming replacement of agricultural production of camomile drug by in vitro culture. For the foreseeable future, hydroalcoholic extracts of high quality camomile varieties produced by agriculture seem to be the only basis of therapeutically valuable remedies.
Selections from the book: “Medicinal and Aromatic Plants III”, 1991.