Comparative analysis of essential oil composition from flower and leaf of Magnolia kwangsiensis Figlar & Noot.

Abstract The essential oils from Magnolia kwangsiensis Figlar & Noot. were obtained using hydrodistillation, and analysed by GC and GC–MS. A total of 31, 27 and 26 constituents were identified in the oils from male flower, female flower and leaf of M. kwangsiensis, and they comprised 99.2, 98.5 and 96.2% of the oils, respectively. Monoterpene hydrocarbons predominated in the oils and accounted for 48.3% of male flower oil, 54.0% of female flower oil and 44.6% of leaf oil. The compositions of flower oils were quite similar but with different content, and were different from those of leaf oil. Graphical abstract

leaves and unisexual flowers in the dioecious individuals (Fu & Jin 1992), flower is white and nearly spherical, and is full of thick aroma. It is valuable to extract natural perfume oils.
Plant essential oils are valuable natural products and frequently used as antimicrobial, anticancer and antidiabetic agents and for their cardiovascular, cosmetic and food applications (Bakkali et al. 2008;Casiglia et al. 2014;Khadhri et al. 2014;Li et al. 2015). Literatures (Hao et al. 2000;Chen et al. 2002;Li et al. 2009;Li 2011;Zeng et al. 2011;Farag & Al-Mahdy 2012) about essential oil of other Magnolia plants showed these plants had plenty of essential oil, and the oil had antioxidant and antimicrobial activities. Study on testa oil from M. kwangsiensis indicated the plant was excellent source of aroma constituents (Huang et al. 2010). At present, information on essential oils from flower and leaf of M. kwangsiensis is very scarce.
Analysis of essential oils in M. kwangsiensis would complement the limited information on the plant applications and guide new perspective on the potential use of their natural products. In this study, the volatile compounds (essential oils) were extracted from flower and leaf of M. kwangsiensis using hydrodistillation and their compositions were analysed and compared.

Results and discussion
Hydrodistillation of male flower, female flower and fresh leaf yielded yellow oils in different yields (0.13, 0.13 and 0.19%, respectively). The volatile oils were analysed by GC-FID and GC-MS. The identified compositions were listed in Table 1. A total of 31, 27 and 26 constituents were identified comprising 99.2, 98.5 and 96.2% of the essential oil from male flower, female flower and leaf of M. kwangsiensis, respectively.
The chemical class distribution of essential oils was also given in Table 1. It could be seen that the three oils of M. kwangsiensis were monoterpene rich. Monoterpene hydrocarbons occupied 48.3% of male flower oil, 54.0% of female flower oil and 44.6% of fresh leaf oil. Oxygenated monoterpenes predominated in the fresh leave essential oil (39.2%). Sesquiterpene compounds constituted 47.4% of male flower oil, 44.1% of female flower oil and 10.5% of fresh leave oil. It should be noted that diterpenes and higher terpenoids were hardly found in all oils. This was likely because that magnoliaceae plants are the most primitive angiosperms (Qiu et al. 1999;Qiu et al. 2000), which commonly contain little or no higher terpenoids. Besides, these results might be influenced by the extraction method. Because diterpenes and higher terpenoids are low volatile compounds, it is very difficult to take these compounds out with water vapour. Literature (Huang et al. 2010) reported α-ocimene (37.3%), d-limonene (9.0%), p-cymene (8.1%) and β-myrcene (7.8%) were major constituents in testa oil of M. kwangsiensis by hydrodistillation. From the obtained results, it was inferred that the different parts of M. kwangsiensis had variance in their essential oils compositions. A-limonene was the most abundant composition in essential oils from fresh male flower and female flower. And limonene is phytochemical with chemopreventive effects on some kinds of cancer and possess antioxidant, antifungal, antimicrobial and immunomodulatory properties (Raphael & Kuttan 2003). Besides, terpinolene and β-myrcene, which existed in three oils, showed antioxidant properties, although some of them showed low activities depending on the mechanism involved in the reaction (Ruberto & Baratta 2000). Those properties suggest that the essential oils from M. kwangsiensis are potential natural resource for utilisation in different industries, such as pharmaceutical, cosmetic and food industry.

Conclusions
A comparative study of the composition of essential oils from flower and leaf of M. kwangsiensis was carried out for the first time. The content of monoterpene hydrocarbons was 48.3% in male flower oil and 54.0% in female flower oil, which was higher than that in leaf oil. B-terpineol was the most abundant constituent in leaf oil and occupied 28.9% of total leaf oil. The presence of biologically active molecules as major components in oils makes M. kwangsiensis become a new potential natural source for production of useful monoterpene compounds which can be used in food and pharmaceutical industry.

Disclosure statement
No potential conflict of interest was reported by the authors.

Funding
This work was supported by the National Natural Science Foundation of China under [grant number 11462001].