Comparative chemical analysis of essential oils from different organs of three Pastinaca taxa

Abstract

INTRODUCTION: Pastinaca sativa subsp. sativa L., Apiaceae (parsnip) is cultivated mainly in the temperate regions of the world because of its edible root. The roots of the best quality are obtained from the plants from the first year, in which this biennial plant usually forms only leaf rosette. In the second year, flowering stems emerge (the plant is cultivated for two years in order to obtain fruits for reproduction). Wild-growing P. sativa subsp. urens (Req. ex Godr.) Čelak. is widely distributed in Europe and P. hirsuta Pančić is endemic in the central part of the Balkan Peninsula (east Serbia, North Macedonia and south and west Bulgaria).

OBJECTIVES: To investigate and compare the composition of the essential oils obtained from roots, leaves, stems, flowers and fruits of cultivated P. sativa subsp. sativa (from the first and/or the second year) and wild-growing P. sativa subsp. urens and P. hirsuta from Serbia.

METHOD / DESIGN: Essential oils were isolated from dried and comminuted plant material by hydrodistillation using Clevenger-type apparatus for 2.5 h. The composition of essential oils was determined by GC-FID and GC-MS and analyzed using multivariate statistical methods: principal component analysis (PCA), non-metric multidimensional scaling (nMDS) and unweighted pair-group arithmetic averages clustering (UPGMA).

RESULTS: Twenty-nine parsnip essential oils were investigated: 11 P. sativa subsp. sativa oils (from four localities; the oils of roots and leaves from both the first and the second year, and of the other organs from the second year), 10 P. sativa subsp. urens oils (from two localities) and eight P. hirsuta oils (from one locality, collected in two different years). Pastinaca sativa subsp. sativa roots from the first year provided the highest oil yields (0.51-0.77%, w/w). The roots of this taxon from the second year (0.02%), and the roots of other investigated Pastinaca taxa (0.10-0.14%) had notably lower oil yields. Regarding other plant organs, high oil yields were generally obtained for fruits (1.40-3.90%) and flowers (0.43-0.93%), and low oil yields for leaves (0.07-0.16%) and stems (0.03-0.13%). In general, 13 to 53 compounds were identified in the essential oils; identified components accounted for 89.4-98.6% of the oils. Phenylpropanoid myristicin was the most abundant in the root essential oils of both investigated P. sativa subspecies (39.7-82.5%). It is interesting to note that the oil of P. sativa subsp. sativa roots from the first year also contained high amounts of terpinolene (14.8-28.7%), which significantly decreased in the oil of this taxon from the second year (1.2%). In P. hirsuta root oils another phenylpropanoid apiole (30.9 and 25.8%) was dominant and the quantities of myristicin were somewhat lower (11.6 and 20.3%). Cultivated P. sativa subsp. sativa leaf essential oils were dominated by myristicin (42.8 and 41.4%) and in the leaf oils of wild-growing parsnips (P. sativa subsp. urens and P. hirsuta), γ-palmitolactone was the most abundant (22.6-47.5%). Additionally, the leaf oils of both investigated P. sativa subspecies contained significant amounts of sesquiterpenes (36.0-46.2%), e.g. (E)-β-farnesene (13.8-22.4%). Compared with the leaf oils, corresponding stem oils were qualitatively similar. However, in the stem oils, the contents of sesquiterpenes were lower [e.g. (E)-β-farnesene 4.9-14.4% in P. sativa oils] and the contents of myristicin (64.9 and 63.3% in P. sativa subsp. sativa oils) and γ-palmitolactone (50.6-60.4% in wild-growing parsnips oils) were higher. The flower and fruit essential oils were dominated by aliphatic esters. The most abundant in P. hirsuta oils were hexyl butanoate (61.9% in the flower oil; 22.0 and 58.4% in the fruit oils) and hexyl hexanoate (17.0% in the flower oil; 59.8 and 29.1% in the fruit oils), and in the oils of both P. sativa subspecies the dominant was octyl butanoate (26.1-31.4% in the flower oils; 53.6-79.0% in the fruit oils). In PCA and nMDS analyses of the oils (except fruit oils), the separation of all three investigated Pastinaca taxa was noticed. The same relations were observed in UPGMA analyses of the leaf, stem and flower oils. In the case of statistical analysis of the fruit oils and UPGMA analysis of the root oils, the samples of two subspecies of P. sativa were grouped together.

CONCLUSIONS: Wild-growing parsnips are equally interesting sources of essential oils as cultivated parsnip. Locality and year of collection did not significantly influence relations among taxa observed in multivariate statistical analysis.