Composition of the Essential Oil from Nuphar pumilum (Timm.) DC. Growing in Russia

Journal of Essential Oil Research: JEOR, Nov/Dec 2005 by Myazawa, Mitsuo, Kawata, Jyunichi, Yamafuji, Chikako

Abstract

The composition of the essential oils from rootstock of Nuphar pumilum has been investigated by capillary GC and GC/MS. In the case of the essential oils of N. pumilum, two chemotypes, Type A (Takasago Yakugyou) and Type B (Yamada Yakkyoku), were observed relative to their contents of elemental sulfur. Type A contained 51 components of which 16.1% were elemental sulfur (S^sub 6^, S^sub 7^, S^sub 8^). The main components were cyclo-S^sub 8^ (13.0%), methyl palmitate (10.1%), methyl linoleate (10.1%), paeonol (7.3%) and β-eudesmol (6.2%). Type B contained 77 components of which 0.6% was elemental sulfur (S^sub 8^). The main components were paeonol (32.5%), eugenol (4.9%), menthol (3.6%), furfural (3.2%) and β-eudesmol (2.6%).

Key Word Index

Nuphar pumilum, Nymphaceae, essential oil composition, cyclo-S^sub 8^, methyl palmitate, methyl linoleate, paeonol, chemotypes.

Introduction

Nupharis Rhizoma ('senkotue' in Japanese) is the dried rootstock of Nupliarjaponicum DC. and Nupliarpumilum (Timm.) DC. It has been long used for diuretic purposes and also as a stomach analgesic in Japanese and Chinese traditional medicines. The genus Nuphar contains many alkaloids. A number of sesquiterpene alkaloids such as nupharidine and deoxynupharidine have been identified from N. japonicum (1-3). Dimeric sesquiterpene thioalkaloids such as G-hydroxythiobinupharideine, 6,6'-dihydroxythiobinupharidine, 6-hydroxythionuphlutine B and 6'-hydroxythionuphlutine B have been identified from the rhizomes of N. pumilum (4). However, there is no report of the volatile components, no has the odor been reported for this Chinese crude drugs. As a result, the volatile constituents of N. pumilum (Russian Nupharis Rhizoma) have been the subjects of this investigation.

Experimental

Plant: Commercially available air-dried rootstock parts (Russian Nupharis Rhizoma) of N. pumilum were obtained from Takasago Yakugyou Co. Ltd. (Type A) and Yamada Yakken Co. Ltd. (Type B).

Isolation of the volatile oil: One hundred grams of dry, coarsely powdered Type A and Type B were separately hydrodistilled using a Likens-Nickerson-type apparatus with diethyl ether as the solvent, to yield 0.092% and 0.029% (w/w) of yellowish green oils and sediments, respectively, which were dried over anhydrous sodium sulphate prior to analyses.

Gas chromatography (CC): GC was carried out using a Hewlett Packard 5890 equipped with a flame ionization detector (FID) on a capillary column, DB-5 (30 m x 0.25 mm, film thickness 0.25 µm). The column temperature was programmed from 60-240°C at a rate of 2°C/min and held 240°C. The injector and detector temperature were 240°C and 280°C, respectively. The flow rate of the carrier gas (He) was 0.679 mL/min. Peak areas were quantified using a HP 3396B integrator on DB-5 column without the use of correction factor.

Gas chromatography/mass spectrometry (GC-MS): GC/MS analysis was carried out with a Hewlett Packard 5972A. GC conditions were the same as previously described. The flow rate of the carrier gas (He) was also the same. The detector interface temperature was set 280°C, with the actual temperature in the MS source reaching approximately 180°C and the ionization voltage 70 eV.

Identification of constituents: The components of the oils were identified by direct comparison of their mass spectral patterns and retention indices (RI) with those published in the literature (5).

Results and Discussion

The oils were analyzed on GC and GC/MS, of which gas chromatograms were shown in Figure 1. The percentage composition and modes of identification of the oils components are listed in Table I. Type A revealed the presence of 51 components, representing 85.7% of the total oil. Type B revealed the presence of 78 components, representing 86.5% of the total oil. Ninety-one components were identified for the first time in this study as components of the oil from N. pumilum. The main components in Type A were cyclo-S^sub 8^ (13.2%), methyl palmitate (10.1%), methyl linoleate (10.1%), paeonol (7.3%) and β-eudesmol (6.2%), and the oil also had lower levels of cyclo-S^sub 6^ and cyclo-S^sub 7^. This oil was interesting because it contained such a high percentage of cyclo-S^sub 8^, which is not commonly found naturally occurring in essential oils. To the best of our knowledge, there is no report of the identification of cyclo-S^sub 6^ and cyclo-S^sub 7^ in any natural essential oil. In a previous report, cyclo-S^sub 8^ was identified in the oils of capers (Capparis spinosa L.) (6) and Allium species (7). It has also been found as a volatile of ham (8). Brevard et al. reported that the occurrence of sulfur in capers did not seem to be connected to fungicide use since the plants used in their study were not typically cultivated but were obtained from \vild growing plants. As reported above, cyclo-S^sub 8^ was a major component of one of the oils of N. pumilum that we analyzed. The main components in Type B were paeonol (32.5%), eugenol (4.9%), menthol (3.6%), furfural (3.2%) and β-eudesmol (2.6%), and the oil contained only a small content of cyclo-S^sub 8^ (0.6%). We consider that the oils from N. pumilum (Russian Nupharis Rhizoma), which contains elemental sulfur, to exist in two chemotypic forms Type A rich in cyclo-S^sub 8^ and Type B poor in the same compounds but rich in paeonol.