Composition of the Oil and Supercritical Fluid CO2 Extract of Sweet Gale (Myrica gale L.) Fruits

Journal of Essential Oil Research: JEOR, Mar/Apr 2005 by Sokolova, Maia, Orav, Anne, Koel, Mihkel, Kailas, Tiiu, Müürisepp, Mati

Abstract

Volatile compounds were isolated from air-dried fruits of sweet gale (Myrica gale L.) using supercritical fluid extraction with CO2 (SFE) and simultaneous distillation and extraction (SDE) micromethod. Extracts were analyzed using GC/FID and GC/MS methods. Sixty compounds were identified representing over 90% of the oil, of which 1,8-cineole (25.7%) and α-pinene (20.6%) were the major components. Two flavonoid compounds were identified in SFE extracts. The composition of SFE extracts under mild conditions did not have great distinctions compared with SDE.

Key Word Index

Myrica gale, Myricaceae, sweet gale, supercritical CO2 extract composition, essential oil composition, 1,8-cineole, α-pinene, myrigalone B.

Plant name

Myrica gale L., Myricaceae.

Source

The plant material was collected from island Saaremaa (Estonia). Voucher specimen was deposited in the Herbarium of the Department of Pharmacy of Tartu University (Estonia).

Introduction

Sweet gale (Mynca gale L.) is a deciduous, bushy shrub, growing to 4 ft high. The wood and leaves smell when bruised. The plant produces flowers in May and June in crowded, stalkless catkins. The leaves are often dried to perfume line, their odor being very fragrant, but the taste bitter and astringent. The branches of sweet gale have been used as a substitute for hops and put into beer. The dried berries are put into broth and used as spice. Also, the leaves are infused like tea, and used as a stomachic and cordial. The fruits of the plant are characterized with very a high content of essential oil and the main attention of this study is concentrated on extraction of fruits.

The oil of sweet gale leaves and flowers has been the subject of many studies (1-9). It can be seen that the composition of the oil can vary quite markedly between different populations of the same species. We did not find the data about the composition of the oil from sweet gale fruits.

In this study, a supercritical fluid extraction with CO2 and a micro simultaneous distillation extraction (SDE) method was used for isolating the volatile compounds from sweet gale fruits. This new alternative extraction technology has been shown to exhibit several advantages in the extraction of natural products from plant material (10-12). The influence of SFE process parameters such as pressure, extraction-time and sample pre-treatment on the oil recovery, have been studied. The composition of SFE extracts was compared with results of SDE method.

Experimental

The sweet gale fruits were collected in July 2000 then dried and stored in a dry place. For each experiment the weight of the raw material was in the range of 0.2-0.4 g for SFE and 10 g for SDE method.

SFE experimentation was performed on Milton Roy SPA (Sample Preparation Accessory) apparatus. The limit operating pressure was up to 34.5 MPa and temperature up to 60°C. Extraction time was varied from 30-90 min. Experiments were carried out at constant temperature 40°C (313 K) and pressure 13.7-27.6 MPa. Collecting solvent was hexane. High purity carbon dioxide 99.5% from AS Eesti AGA was used. The yield of the SFE extract was determined by weighing receiver-tube before and after SFE procedure.

For oil isolation from sweet gale fruits by SDE method, Marcusson's micro-apparatus (13) with hexane as the solvent and tetradecane as the internal standard was used. The distillation time was 2 h and the yield 1.2% (12 mg/g) of sample initial weight from whole fruits was obtained.

GC analyses were performed using Chrom-5 chromatographs with FID on two fused silica capillary columns (50 m x 0.2 mm) with bonded stationary phases OV-101 and PEG 20M. Helium, the carrier gas, with split ratio about 1:150, flow rate 1.3-1.5 mL/min was applied. Temperature programming was from 50°-250°C (OV-101) and 70°-230°C (PEG 20M) at 2°C; injector temperature was 160°C. A Hewlett Packard Model 3390A integrator was used for data processing. Identification of the oil components was assigned by comparison of their retention indices (RI) on two columns with the RI values of our data bank and with literature data, and by their mass-spectra. The quantitative composition of individual compounds in the oil and the SFE extract was determined by the internal normalization method.

The mass spectrometric analyses were carried out on a Hitachi M-80 B gas chromatograph double focusing mass spectrometer using RSL-150 Heliflex (35 in x 0.25 mm) fused-silica capillary column. The column temperature was 1 min at 60°C, then 60°-180°C at 5°C/min, then 180°-300°C at 10°C/min and 10 min at 300°C.

Results and Discussion

The effect of pressure on the yield of volatiles from the fruit of sweet gale using SFE method is presented in Figure 1. The yield was increased about three times with increasing the extraction pressure from 13.7 to 27.6 MPa at 40°C after 60 min extraction, as can be seen in Figure 1.

The effect of extraction time on yield was also investigated. Extraction time was varied from 30 to 90 min under different pressures. It can be considered that the optimal extraction time was 60 min (Table I).