| Litsea cubeba (Lour) Per. is one of the important resources of aromatic plant with fruits rich in essential oils. The dominant components in the Litsea cubeba essential oils are monoterpenes and sesquiterpenes. Composition of essential oils and essential oils content may vary with climatic, edaphic, topographic conditions and breed. To investigate the diversity of different population, the chemical composition of Litsea cubeba essential oils and essential oils content were determined for mature fruits harvested from eight main distribution areas in China. The essential oils were obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry. The relative amounts of individual components were calculated via peak area normalization. At the same time,16batches of mature fruits in the distribution areas were chosen as samples. Standard fingerprint of Litsea cubeba essential oils was developed by using GC-MS. Chemometrics methods were employed to recognize the fingerprint established. This work lays a theoretical foundation for exploring and utilizing the Litsea cubeba essential oil. The result showed as follows:(1)The overall content of Litsea cubeba essential oils in different distribution areas were ranged from3.04%to4.56%, with an average of3.59%. The essential oils content were highest in Jingdong and lowest in Fenyi. There was no significant difference of essential oils content among Litsea cubeba fruits of Jianou, Yongan, Anyuan, Fenyi, and Yongzhou. However, significant difference was found in essential oils between Bijie and Jingdong. Moreover, highly significant difference existed in essential oils between Changning and Jingdong.(2)GC-MS analytical conditions for essential oil of Litsea cubeba were established as follow: HP-5MS capillary column (30m×0.25mm internal diameter,0.25μm film thickness) The column temperature was set at50°C for2min, ramped at a rate of3°C·min-1to120°C for2min, then increased to250°C at15°C·min-1for5min High purity helium was used as the carrier gas at a flow rate of1mL·min-1, with column pressure of50kPa The sample was diluted in the ether (1:10) and a volume of1.0μL was injected Solvent delay time of4minutes The injector was held at220°C and operated in the split mode at a ratio of1:40The MS operating parameters: EI electron source Ionization voltage of70eV Scan range of30–550amu Quadrupole temperature of150°C Ion source temperature of230°C Interface temperature of260°C Electron multiplier energy of1024V. (3)According to GC-MS analysis of the chemical composition of fruit essential oils taken from eight distribution areas,59compounds were identified, including41of monoterpenes,15of sesquiterpenes, and3of non-terpenes. Furthermore, o-cymene and eremophilene were isolated in essential oils of Litsea cubeba for the first time. Quantitative analysis showed the major components in Litsea cubeba essential oils from all distribution areas were monoterpenes (94.4%–98.4%), represented mainly by α-citral and β-citral (78.7%–87.4%). The content of α-citral was always higher than that of β-citral. Compared with the previous report, the content of limonene was a bit lower on the whole.(4)Sixteen batches of essential oils of Litsea cubeba fruits were analyzed by GC-MS, by which standard fingerprint of Litsea cubeba essential oil was also developed. Principle component analysis and cluster analysis methods were employed to recognize the fingerprint established. Twenty-seven peaks were found in the16batches of samples, among which18peaks were determined. The similarity analysis was conducted based on the27peaks. Validation of the method, principle component analysis and cluster analysis were preformed according to the18peaks. It showed that the similarity degrees of all samples were more than0.98, and the method was proved to be applicable for analyzing the fingerprint. The principle component analysis was relatively consistent with that of cluster. The result indicated that the GC-MS fingerprint for Litsea cubeba essential oil here was stable and reliable. And the diversities of Litsea cubeba essential oil were observed not only in different distribution areas but also in the same distribution ones in the light of the chemical pattern recognition. |
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