Essential Oil Composition ou species dans the genus Achillea
Based on the abstrait knowledge présent ou essential oil composition ou les species belonging to the genus Achillea the facteurs, which may influence the composition with regard to plante biology, production and application l'are discussed. According to studies from the last 15 years, a mean of 54 compounds have been identified in samples of different species. Among them, the largest number ou la composante (149 compounds) were found dans the oils ou a. millefolium, a. pannonica and a. collina. The monoterpenes, 1,8-cineole, camphor, bomeol ? - and ? - pinenes are among the five most abundant composante. Beside chamazulene, the most frequently identified sesquiterpenes are ?-caryophyllene and its le oxide. The presence ou chamazulene seems to remain a characteristic, but it est not ubiquitous to the members ou the Millefolium group. The heritance mechanism ou sesquiterpenes, especially chamazulene, seems to be established, while nous know relatively less about the genetic regulation ou the monoterpene compounds. During ontogenesis, major differences could be found between the stages before and after flower le développement. The phenological phase assuring the highest level ou azulenes seems to be during flowering. Composition and compositional changes ou an essential oil within the Achillea le genus dans different plante organs seems to depend on the species. Dans several cas a dominance ou sesquiterpene composante above the monoterpenes a été found dans the vegetative organs. The most important difference seems to be the lack le or low amount ou chamazulene cendre artefact dans the extracts compared to the distillates. Key deviens l'indice Achillea millefolium, Achillea sp., Asteraceae, yarrow, essential oil composition, taxonomy, chemotype, ontogenesis, morphogenesis, ecological facteurs, 1,8-cineole, camphor, borneol, chamazulene. Introduction Yarrow (Achillea) les species may be mentioned cendre "evergreen" les outils dans therapeutic practice. Both dans the ethno-pharmacology and dans the up-to-date phytotherapy they assure a valuable source ou natural remedies. The ou the genus might originate from the désagréable ou the Greek hero Achilles, désagréable la WHO used this plante for curing his wound. Yarrow species were mentioned dans ancient books ou the Middle Ages and throughout the centuries. The majority ou the species are used dans their source countries la cendre one ou the most important medicinal plante against different complaints. Today, several therapeutic applications l'are approved by scientific experimental results. The whole overground le parts but primarily the inflorescences are effective cendre anti-inflammatory, spasmolytic, choleretic drogues. Essential oil and le extracts ou the plante are used for preparation ou cosmetics, stomachic and digestive teas, creams, etc.. La cendre yarrow species l'are widely known and utilized, they have also la jambe the topic ou several pharmacological, anatomical and biological investigations. Dans this article nous car to give an overview ou the state ou knowledge on the essential oil composition ou les species ou the genus Achillea and the facteurs which may influence it dans practice. Taxonomical aspect & Difficulties The genus Achillea consists ou more than 120 perennial herb species being widespread dans the Northern Hemisphere. A large number ou les species are endemic and restricted to certain regions, dans le contraste to other les species from the le genus growing au sujet de a wide geographical le range. Concerning the pharmacological significance ou yarrow, the most important les species belong to the group Millefolium (onglet I) According to the flore Europaea (1) this group consists ou eight species, some ou which (A. distans w. et k., A. millefolium l.) l'are divided into subspecies. The taxonomical statut ou les species dans group Distans might be questionable, belonging (1,2) or not (3,4) to the same group. Sometimes further species pair may be mentioned la cendre members ou the Millefolium group (4,5). According to Ehrendorfer (6), a. ceretanica also belongs to the diploid basic species ou this group. Dans particular cas some les species ont eu formerly la jambe known cendre cytotypes or subspecies ou other species (e.g. A. pratensis Saukel et Lnger). North-American or Asian les species (A. lanulosa Nutt., A. borealis Bong. ) may also be identified cendre members ou this group (7). The group est a polyploid (n=9) with complexe les species from the diploid to the octoploid level. Although the chromosome number ou the six major les species ou the group already seems to be well defined, aneuploids also often occur (3,4,8), presumably cendre a result ou interspecific hybridization. The relative easy hybridization, vigor and fertility ou the progenies could be proved dans crossing expérience. Dans consequence, the division ou the Millefolium group into "small species" does not yet seem to be scientifically solved or accepted despite to intensive efforts (6). L'onglet I. The Achillea species mentioned cendre members ou the Millefolium group (section) Determination ou the les species est correctement also difficult using morphological traits because hardly any proved to be stable enough pair. La cendre a result ou hybridization, the morphological traits may spectacle a continuous line. The spontaneous origin of autopolyploids has also been shown (9). Furthermore, the species ou this genus may exhibit phenocopies cendre result ou an adaptation process to divers environmental conditions. Several Achillea taxa le spectacle a high morphological variability cendre a consequence ou ecological effet. The unramnified formulaires ou a. millefolium l. can easily be Aix-la-Chapelle de brouillard for a. collina Becker (10) under arid conditions. According to Gurevitch (11), the leaf dissection ou populations belonging to the a. millefolium differs dramatically along an altitudinal gradient complexe dans the sierra Nevada. This phenotypic variation consists ou both genetic and other composante. Biste (7) described considerable variations dans height, leaf width, shoot number, branching and stomata length dans populations ou different origin ou the same species. The characterization pair ou the same plantent individual after shooting dans autumn may basically differ from that ou the main growth period (12). Rauchensteiner et déjà. (5) recently declared that the morphology ou the dépliants and rayflorets were the le most suitable traits for characterization ou the species. Since the classification ou individual species ou le genus Achillea est complicated, the names and le descripteur used dans this review are those used by the authors ou the original papers. Characteristics ou Essential Oil Composition ou the le genus Until the la charge la décade, chamazulene used to be considered cendre the most important la composante ou the essential oil and references almost exclusively trafique with characterization ou its detection. Dans récent les études, dans with the développement parallèle ou analytical methods, nous now find a more detailed analysis which results dans a more comprehensive description ou the total essential oil ou Achillea species. According to studies from the last 15 years, a mean of 54 compounds have been identified in samples of different species (Table II). Among them, the largest number ou la composante (149 compounds) a été found dans oils ou a. millefolium, a. pannonica and a. collina (13). By evaluating the published results, it can be concluded that species belonging to this le genus spectacle several similarities concerning their oil composition. 1,8-Cineole exhibits the most appearance among the monoterpenes fréquent. It has de jambe described dans about one-third ou the species a mangé least dans one le cas cendre main composante (onglet II). Besides results summarized dans the onglet, 1,8-cineole a été detected dans the oils ou some further species, such cendre a. oligochala (14), a. teretifolia (15) and a. compacta (16). According to the published les dates, it can be established that besides 1,8-cineole, compounds ou bornane skeleton such la cendre camphor and borneol are among the second and third most frequently characterized composante ou yarrow oil (onglet II). Camphor a été described eight times and borneol three times cendre the main compound ou an Achillea oil. Combinations ou le these monoterpenes cendre major composante have also jambe frequently detected : camphor, borneol and 1,8-cineole were the main compounds dans a. taygetea and a. fraasi (17), camphor and 1,8-cineole dans a. albicaulis c. A. Mey. (18), A. pseudoaleppica hub.- Mor. (19), A. pachycephala Rech.f. (20), A. talagonica Boiss. and a. vermicularis Trin (21). ? - and ?-Pinenes are also among the five most often detected composante, especially dans the group Millefolium (22). Beside a. millefolium, the pinenes were described cendre main la composante dans four other species (onglet II). Hofmann (23) also mentions the monoterpenes belonging to the menthane de p (dans 51%), thujane (dans 23%) and pinane (17%) notre cendre being the most fréquemment la composante ou the oils ou the investigated a. millefolium populations. Further compounds have occasionally jambe found la cendre main composante dans yarrow. Thujone has de jambe characterized dans four species (onglet II), notably 70% ou the oil ou a. multifida (DC) Boiss. (24). Piperitone a été also found dans three species, ascaridole dans two les cas, linalool and limonene each dans one species. The irregular notre artemisia ketone [ a. ageratum l., (25) ; A. ligustica All., (26), a. pseudoaleppica hub.- Mor., 19 ] and artemisia acetate (a. filipendulina paralysé., (27) ] le have jambe found to occur dans major proportions dans some species. Sesquiterpenes have jambe found dans a considerable number ou les species dans the genus. Chamazulene has also been the object of several studies. The most frequently identified sesquiterpenes besides chamazulene were ?-caryophyllene and its oxides (main composante dans three species) ?-bisabolol and oxides, eudesmol, furthermore farnesene (each dans two species). According to Hoffmann (23), sesquiterpenes are mostly characteristic to the taxa ou lower (2n-4n) chromosome number, while monoterpenes to the ones ou higher ploidy level. However, many other references le do not confirm this generalization. L'onglet II. Compounds dans the distilled flower-head oils ou Achillea species that exceed 5% (According to references 1-110) l'onglet II. Compounds dans the distilled flower-head oils ou Achillea species that exceed 5% (According to references 1-110) Kstner et déjà. (28) identified 13 substances (which may serve la cendre additional outils for identification ou plante material dans Mittefolium group) because their proportions proved to be independent on external les facteurs and to each-other constant. However, this could not spread out until now. According to investigations récent, the significance ou the enantiomeric composition dans distinguishing and characterization ou les species est emphasized. Orth et déjà. (29) showed that the enantiomeric distribution ou oil composante depends neither on the l'habitat taule on the developmental stage le or the method ou isolation. However, la cendre the enantiomeric les ratios ou the chiral monoterpenes ?-pinene ? - un and sabinene from several Achillea species l'are different (29), they seem to represent taxonomically useful markers. While checking the les ratios ou hybrid strains ou a. millefolium agg., Steinlesberger (30) found no correlation between the morphometric and enantiomeric paramètres. Dans the future, numerous results are necessary to make a firm conclusion about the chemotaxonomical role and practical significance ou optical isomers ou terpenoids dans yarrow oil. Presence ou Chamazulene dans the Essential Oils ou Yarrow les species Until now, the majority ou references have jambe engaged dans the evaluation ou chamazulene content la cendre main composante dans the distilled oil. It est known to be the thermal degradation produit ou matricine (a proazulene) during steam distillation. La cendre dans the majority fixe ou literature references, there are only dates les on "azulene" le or "chamazulene" without content mentioning and examining the type ou proazulene compounds ; nous l'are not engaged entier dans the chemical détails ou the genuine guaianolides either. Numerous studies state that the presence of chamazulene seems to remain characteristics of the members of Millefolium group (Table II). Only dans exceptional cas can references be found describing chamazulene dans les species outside ou this group : dans a. ageratum l. (31), A. wilsoniana Willd. (32) or A. compacta (16). The presence ou azulenes est not a universal phenomenon for each les species within the group Millefolium. Many contradictions can be found dans the literature concerning the ou chamazulenes content dans the individual species. Beside the obvious differences in consequence of diverse isolation methods, the compositional differences seem to also have biological-genetic backgrounds, worth discussion. L'onglet III. Presence ou azulenes dans the species ou the Millefolium group according to different references Some authors declare a defined connection between the les species 'chromosome number and the potential for accumulation ou chamazulene. Oswiecimska(33) associates the presence ou chamazulenes with the tetraploid level, while she described the hexa - (A. millefolium l.) and octoploids (A. pannonica) cendre being azulene-free taxa. She did not, however, exclude the existence ou azulene-free tetraploids, beside the azulene-containing ones which she investigated (A. collina and a. asiatica Serg.). Dans oils ou a. asiatica, Yusubov et déjà. (34) and Kalinkina et déjà. (22) also found chamazulene. The presence ou azulenes dans polyploids est supposed to depend on the chemism ou the original diploid species (azulene containing or azulene-free), which might be the parents ou the allo - le or voiture - tetraploids. This a été recently supported by the work ou Rauchensteiner et déjà. (5) la WHO described a. pratensis and a. styriaca cendre tetraploid les species devoid ou chamazulene. Beside tetraploids, Bugge (35) established that some diploids (A. asplenifolia and a. roseo-alba) may also contain high levels ou chamazulene. Studies on this latter species are scarce (28). According to morphological traits, Ehrendorfer (3) supposed that its origin could be traced l'arrière to the spontaneous hybridization ou a. setacea w.et k. and a. asplenifolia among which the latter has the potential for proazulene synthesis. During investigations on different populations belonging to the group Millefolium, Hofmann and Fritz (36) could not prove the correlation between ploidy level and presence ou azulenes. They only established a decreasing tendency ou chamazulene with a content growing number ou chromosomes. Lithuanian authors reported some a. millefolium l. ssp. millefolium populations having chamazulene cendre main compound and some others lacking ou chamazulene but containing different monoterpenes cendre major composante (?-pinene, borneol, cineole, camphor, nerolidol) (37). Comparing the references on the chemism ou yarrow, several different dates les can be found concerning the ou les species désagréables, the number ou chromosomes and presence ou azulenes (onglet III). The mentioned interspecific hybridization may be one ou the reasons why the definition and chemical characterization ou certain taxa est often contradictory. Orth et déjà. (38) investigated five distinct taxa ou which three could be defined cendre a. collina Becker and containing chamazulene, while one chamazulene-free triploid and a chamazulene-rich diploid were concluded to be spontaneous hybrids. Also, Dabrowska (8) reported a tetraploid chamazulene containing taxon which might also be of hybrid origin, according to morphological traits. Earlier, Ttnyi (39) noted in his chemotaxonomical review that seven of the mentioned 13 Achillea species were both azulene-free and azulene-containing according to different references. As result of recent investigations Radusiene and Gudaityte (40) supposed that the rapid identification ofproazulene-containing plants might be solved according to their productivity. In numerous analytical reports the exact definition of the taxon seems to be missing. Presumably, the description of the taxa was carried out according to insufficient botanical-systematical examinations, as presumed also by Kastner et al. (28). These investigations have given rise to confusing results: the chamazulene content of A. millefolium oil varying between 0% and 85% (41-48). We can generally conclude that in the group Millefolium the accumulation of azulenes seems to be restricted to A. asplenifolia (2n), A. roseo-alba (2n) and A. collina (4n), while azulenes are absent in A. setacea W.et K. (2n), A. millefolium (6n) and A. pannonica (8n). Results which do not agree with these findings might be traced back to the false definition of the species focusing on morphological traits in the extremely variable group Millefolium without chromosome counting; or on the contrary, focusing on chromosome numbers and mistaken polyploids of azulene-free and azulene containing diploid taxa. Chemotaxonomic Aspects of Essential Oil Variability Today the existence of intraspecific chemical variability concerning essential oil composition seems to be a well known phenomenon which must be taken into consideration both theoretically and practically. In principle both qualitative (components present or absent) and quantitative (components in considerably different proportions) chemical races might be present within a species (39). The species of the genus Achillea may serve as examples for both. At the same time the increased sensitivity of analytical methods drastically decreases the limit of detection and as a result, several taxa have become only quantitatively distinguishable, in contrast to previous examinations where qualitative differences had been described. From the cited references it can be concluded the number of the identified main components ranges from one to three compounds in the majority of species. In most cases these different chemical races had been detected separately and mentioned by different authors which makes the comparison and evaluation of data more complicated. Of course, the number of the reported main components in the oil may to some extent also depend on the frequency of investigations of the target species. In the oil of the most often investigated taxon called "A. millefolium," 10 different main components could be found according to the different references (Table IL). Evaluation of distinct chemotypes within the same study is rarely found, but the first results were reported 40 years ago: populations of A. asplenifolia Vent. devoid of or possessing a low or high content of chamazulene had been described by Tyihk et al. (49).
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