Chemical Composition of the Essential Oil of Ligularia dictyoneura

Abstract

The genus Ligularia (Fam. Compositae) includes approximately 150 species [1], most of which are distributed in China [2–4], and it is a rich source of furanoeremophilanes and related sesquiterpenes [5]. Ligularia dictyoneura (Franch.) Hand.-Mazz. grows commonly in the waterside, underbrush, slope, and grassland. It ranges from 1900–3600 m in altitude [6], and the intraspecific diversity of L. dictyoneura is extremely high [7]. To our knowledge, this is the first report on the chemical composition of the essential oil of L. dictyoneura. The flowering aerial part of L. dictyoneura was collected in August 2010 of Wenshan County, Yunnan Province, China. The species was identified by Assoc. Prof. Jiang-hua Liu (Southwest Forestry University, Kunming City, Yunnan Province, China). A voucher specimen (No.100502) is deposited in the Key Laboratory for Forest Resources Conservation and Utilization in the Southwest Mountains of China, Southwest Forestry University, Kunming City, Yunnan Province, China. The sample was kept from direct light and air-dried at room temperature. Hydrodistillation was carried out under atmosphere pressure and used for 6 h to extract the essential oils. The distillate was extracted with ether and then frozen at –4 C to the dry essential oil. The essential oil of the aerial part of L. dictyoneura gave a yield of approximately 0.3% (w/w). The analysis was carried out using an Agilent 6890N-GC gas chromatograph with a fused silica capillary column (American J & W. HP-5 30 m 0.25 0.25 m) coupled to a mass selective detector (MSD-5973N) with electron ionization 70 eV. The carrier gas was helium (99.999%), and the flow rate was 1 mL/min. The oven temperature was from 80 C to 290 C at 4 C/min and held at 290 C for 30 min. The components were identified by comparison of their mass fragmentation with those of the NIST02 mass spectra library. Component relative percentages were calculated on the basis of GC peak areas. The constituents of essential oil from L. dictyoneura are listed in Table 1 in order of their elution time from the HP-5 column. A total of 37 compounds was identified in this species, accounting for 100% of the essential oils. The components were composed mainly of sesquiterpene, monoterpene, and alcohol. The samples were dominated by the sesquiterpene (50.6%), including caryophyllene oxide (26.3%) as the main component. The monoterpene (15.7%) was the next major component, including -phellandrene as the main component. The alcohol was the third main component (12.4%). The chemical constituents of essential oils from Ligularia genus, such as L. fischeri [8], L. przewalskii [9], L. myriocephala [10], L. jaluensis, L.mongolica [11], L. tongolensis [12], L. melanocephala [13], L. virgaurea [14, 15], L. sagitta [16], and L. veitchiana [17] are different according to the literature.