Achillea millefolium L. ssp. millefolium (Yarrow)

2015

Distribution and Importance

Yarrow, commonly called soldier’s woundwort or herb of the good Lord, owes some of its common names to its known pharmacological, antihemorrhagic, and sedative properties. Dioscorides went even further in the applications of this plant; it can be used not only as a vulnerary, but also has tonic, antispasmodic, antipyretic, and antimycotic properties. Also, the scientific name of the plant is related to its antihemorrhagic action. According to the Greek legend, during the Trojan War (ca. 1250 B.C.), Achilles healed the wounds of King Telephos with yarrow; thus, the name Achillea, millefolium indicates that the leaves are finely divided.

A. millefolium (Compositae) is a herbaceous, perennial plant that can reach 30-60 cm in height. Commonly scented, it usually presents white flowers. The leaves are greenish-gray due to the numerous trichomes. The plant is common throughout Europe, western Asia, Siberia, and North America, growing wild in fields, woods, and pastures. The flowering period extends from May to October. It is harvested from early to late summer, and is used either fresh or dried. The essential oil from the leaves, particularly that from the flower heads, is the source of its medicinal properties. The presence of azulenes is particularly important because of their antiinflam-matory and antiedematous properties. For this reason, when blue chamomile oil is scarce, yarrow oil is commonly found as its adulterant.

The popularity of yarrow has changed over the years. Its virtues were first recorded by Dioscorides, but since then they have also been acknowledged in several publications, in books on medicinal and aromatic plants and in pharmacopoeias. Several American Indian societies in North America used yarrow, particularly A. lanulosa, in the treatment of bruises, sprains, and swollen tissues. The plant was also a popular antipyretic, having also analgesic and anti-inflammatory effects. The application of yarrow to heal battle wounds was also recorded during the US Civil War. In Portugal, Feijao (1954) referred to its use as an infusion because of its tonic and antispasmodic activities and, externally, due to its vulnerary effect. The dried leaves and flower heads were officially given in the United States Pharmacopoeia from 1836-1882, for tonic, stimulatory, and emmenagogic purposes. Yarrow is presently listed in the pharmacopoeias of Austria, Hungary, Poland, and Switzerland under Aetheroleum millefolii and Millefoliiflos (Pharmacopoeia Hungarica 1970; Pharmacopoeia Helvetica 1979-1991; Martindale 1989).

Apart from the various medicinal uses, yarrow has been used in the production of liqueurs, beers, and shampoos and it is still commonly used as a tisane due to its antispasmodic activity.

Chemical Constituents

From a chemical point of view, several types of compounds have been found in the genus Achillea, among which are amides, flavonoids, sesquiterpene lactones, and various volatile compounds present in the essential oils.

The A. millefolium complex has been particularly studied since it consists of a group of difficult to distinguish species. In Europe, its representatives include A. millefolium, A. pannonica, A. collina, A. aspleniifolia, and A. setacea. Their broad morphological and cytological diversity as well as their commonly encountered phenotypic plasticity led to the general use of the term “yarrow“.

An important compilation of the ethnobotany and phytochemistry of this complex was performed by Chandler et al. (1982). A. millefolium L. s. str. includes only the hexaploid representatives with 2n = 54. The presence or absence of azulenes is still a matter of controversy. While some authors consider that A. millefolium L. s. str. (hexaploid) does not contain azulenes, others describe their presence, although in minimal amounts. Also in this species, amides, flavonoids, sesquiterpene lactones, and triterpenes have been found. Several of these compounds have been tentatively used to compare and separate different elements of the A. millefolium complex. Studies on the composition of their essential oils have also been used as an additional characteristic of differentiation. One of the most important studies on the composition of the essential oil from flower heads of A. millefolium was published by Falk et al. (1974), who identified 24 components. Since the review of Lawrence (1984), studies on the essential oil of A. millefolium have mainly dealt with the proazulene content and the ploidy level. In a recent paper on the essential oil from the aerial parts of plants belonging to the A. millefolium L. complex, Hachey et al. (1990) identified 60 components, 40 of which were reported for the first time. It is noteworthy that the authors reported, for the first time, β-thujone as the major component of the oil of A. millefolium. The same authors identified ten nonterpenoid compounds, not previously reported in these oils. Although it is difficult to define a chemotype within the A. millefolium complex, Eglseer et al. (1988) have suggested that the relative amounts of α- and β-pinene, caryophyllene, sabinene, 1,8-cineole, camphor, and chamazulene in the essential oil may serve as distinguishing criteria. According to Motl et al. (1990), the amount of germacrene-D could also be used as a marker.

Summary and Conclusion

As A. millefolium is an aromatic plant with known pharmacological properties, the objectives of this work were:

(1) the establishment and mass cultivation of a cell line and determination of the parameters for good growth;

(2) the ultra-structural study of the glandular trichomes of the plant and of the cell suspension cultures during growth;

(3) comparative analyses of the essential oils formed in vivo and in vitro.

The composition of the essential oil from the cell suspension cultures differed markedly from that of the parent plant. These differences are most probably related to the in vitro conditions. Nevertheless, the ultrastructural study of the cell suspension cultures, together with the recognition that the cells in vitro produced monoterpenes, sesquiterpenes, and phenylpropanoids, suggests that at least part of the secretory characteristics of A. millefolium were expressed in vitro. Furthermore, it is also relevant that the cells in vitro produced demethoxy-encecalin, a compound of biological interest that was not found in the parent plant. This makes the cultures an interesting model for a study of the in vitro production of this compound.

Selections from the book: Medicinal and Aromatic Plants VIII (1995).