Constituents of Essential Oil of Zingiber nudicarpum from Vietnam (original) (raw)

2019, Chemistry of Natural Compounds

Zingiber Mill. is a genus of gingers found in pantropical Asia. The genus comprises about 144 species, ranging from India to Japan and Southeast Asia, with the center of biodiversity of the genus residing in the Indochinese Peninsula and southern China [1]. Currently 32 Zingiber species are known from Vietnam [2]. Zingiber nudicarpum D. Fang was recently discovered and collected in the forest protected areas in Pu Huong and Pu Hoat Nature Reserves [3]. It is a rhizomatous herb up to 2.8 m tall, forming small clumps, with up to six leaf shoots per clump [3]. To date, the authors are not aware of any literature citation on the volatile composition of Z. nudicarpum. The aim of the present study was to report the chemical compounds identified in the essential oils obtained from the leaf, root and fruit of Z. nudicarpum grown in Vietnam. In recent times, the volatile constituents of some Vietnamese plants have been published [4, 5]. The leaves, roots, and fruits of Z. nudicarpum were collected from Pu Hoat Natural Reserve, Nghe An Province, Vietnam, in August 2014. A voucher specimen, NDH 474, was deposited at the Botany Museum, Vinh University, Vietnam. Plant samples were air-dried prior to extraction. Hydrodistillation was carried out separately in an all-glass Clevenger-type distillation apparatus according to established procedure [6]. The volatile oils distilled over water and were collected in the receiver arm of the apparatus into a clean and previously weighed sample bottle. The oils were kept under refrigeration until the moment of analysis. Gas chromatography (GC) analysis was performed on an Agilent Technologies HP 6890 Plus Gas chromatograph (HP-5MS column, 30 m × 0.25 mm, film thickness 0.25 μm). Temperature parameters: column oven 40°C, injection pot-250°C, detector-260°C. Time programming: 40°C for 2 min, temperature rose to 220°C (10 min hold) at 4°C•min-1 , carrier gas H 2 (1 mL•min-1), split ratio 10:1, volume injected 1.0 μL. Inlet pressure, 6.1 kPa. Each analysis was performed in triplicate. Retention indices (RI) of each component was determined relative to the retention times of a homologous n-alkane series with linear interpolation on the HP-5MS column. Gas chromatography-mass spectrometry (GC/MS) was performed on an HP 5973 MSD mass spectrometer with HP 6890N Plus GC (HP-5 MS, 30 m × 0.25 mm, film thickness 0.25 μm). MS conditions: ionization voltage 70 eV; emission current 40 mA; acquisitions scan mass range 35-350 amu, sampling rate 1.0 scan•s-1. Most constituents were identified by gas chromatography by comparison of their retention indices with those in the literature or with those of available authentic compounds. The retention indices were determined in relation to a homologous series of n-alkanes (C 8-C 24) obtained under the same operating conditions. Further identification was made by comparison of their mass spectra with those stored in the library [7], peak enrichment on co-injection with authentic standard where possible are as described previously [4, 5]. The yields of the hydrodistilled essential oils of Z. nuricarpum were 0.20% (v/w, leaves), 0.35% (v/w, roots), and 0.51% (v/w, fruits), calculated on a dry weight basis. Table 1 indicates the percentages and identities of compounds present in the oils.