Essential Oil of Betula pendula Roth. Buds

The essential oil of Betula pendula Roth. buds was obtained using both hydrodistillation and microdistillation techniques and their chemical compositions were analyzed using both gas chromatography (GC) and gas chromatography–mass spectrometry (GC-MS). Overall, more than 50 compounds were identified representing 80% and 92% for hydrodistillation and microdistillation, respectively. The main components (by hydrodistillation and microdistillation, respectively) found were α-copaene (12% and 10%), germacrene D (11% and 18%) and δ-cadinene (11% and 15%) in the analyzed essential oils. The microdistillation technique proved to be a useful tool and compliant alternative when compared to hydrodistillation.

The essential oil of Betula pendula Roth. buds was obtained using both hydrodistillation and microdistillation techniques and their chemical compositions were analyzed using both gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Overall, more than 50 compounds were identified representing 80% and 92% for hydrodistillation and microdistillation, respectively. The main components (by hydrodistillation and microdistillation, respectively) found were ␣-copaene (12% and 10%), germacrene D (11% and 18%) and ␦-cadinene (11% and 15%) in the analyzed essential oils. The microdistillation technique proved to be a useful tool and compliant alternative when compared to hydrodistillation.

Keywords: birch -Betula pendula -Betulaceae -essential oil -GC -GC-MS -hydrodistillationmicrodistillation
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Plant Material
Buds were collected from Maxhütte, Regensburg in April 2002. The plant material was air dried in a shady and aerated room until the weight was stable.

Isolation of the Essential Oil
The air dried buds were crushed using a mortar and were subjected to both hydrodistillation and microdistillation.

Hydrodistillation
The plant material was hydrodistilled for 3 h using a Clevenger type apparatus. The essential oil yield was calculated on dry weight basis corresponding to 0.5% (v/w).

Microdistillation
The plant material (~200 mg) was placed in the sample vial of the MicroDistiller® (Eppendorf, Germany) system together with 10 ml of distilled water. NaCl (2.5 g) and water (0.5 ml) were added into the collection vial to break any possible emulsion formation. Hexane (300 l) was also added into the collecting vial to trap the volatile components. The sample vial was heated to 100ЊC at a rate of 20ЊC/min and then kept at 100ЊC for 15 min. It was then heated to 112ЊC at a rate of 20ЊC/min and kept at this temperature for 35 min. Later, the sample was subjected to post-run for 2 min under the same conditions. The collecting vial was cooled to -5ЊC during the distillation. After the distillation was completed the n-hexane-trapped volatiles were analyzed by both by GC and GC-MS.

Gas chromatography
The oils were analyzed by GC using a Hewlett Packard 6890 system. An HP-Innowax FSC column (60 m ϫ 0.25 mm, with 0.25 m film thickness) was used with nitrogen as carrier gas (1 ml/min). The oven temperature was kept at 60ЊC for 10 min and programmed to reach 220ЊC at a rate of 4ЊC/min, then kept constant at 220ЊC for 10 min before proceeding to 240ЊC at a rate of 1ЊC/min. The split ratio was adjusted to 50:1. The injector temperature was set at 250ЊC. The percentage compositions were obtained from electronic integration measurements using flame ionization detection (FID), also set at 250ЊC. n-Alkanes were used as reference points in the calculation of relative retention indices (RRI). Relative percentages of the characterized components are given in Table 1.

Gas chromatography-mass spectrometry
The essential oils were analysed by GC-MS using a Hewlett-Packard GCD system. Innowax FSC column (60 m ϫ 0.25 mm, 0.25 m film thickness) was used with helium as carrier gas (1 ml/min). GC oven temperature and conditions were as described above. The injector temperature was at 250ЊC. Mass

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Chemical composition of essential oil of B.pendula

Results and Discussion
The air dried crushed buds of B.pendula were utilized to obtain volatiles by means of hydrodistillation and microdistillation. The essential oils were further analyzed both by GC and GC-MS systems using a polar column, resulting in the identification of 50 constituents in the hydrodistilled sample, representing 80% of the total essential oil. The essential oil yield was 0.5% (v/w) in this case, low when compared to other previously investigated samples (15)(16)(17)(18). In total, 53 constituents were identified in the microdistilled sample, representing 92% of the oil as seen in Table 1. Overall, sesquiterpene hydrocarbons were found in both samples as the dominating group of compounds. ␣-Copaene (12% and 10%), germacrene D (11% and 18%) and ␦-cadinene (11% and 15%) were identified as the main constituents for the hydrodistilled and microdistilled samples, respectively. However, comparison of both samples suggested that both techniques resulted in a similar composition of the volatiles obtained. In this study, the essential oil profile of B.pendula obtained from the buds was quite different from that of previous investigations and results (15,17,18). In earlier studies betulenols were found to be the major constituents in the volatile oil of B.pendula (15,17,18,22). Kaneko et al. (10) also reported ␦-cadinene (9.6%) as the main constituent of B.pendula from Japan. Microdistillation was utilized here as a useful method enabling the analysis of ~200 mg samples of plant material for its volatiles compared to the hydrodistilled essential oil. This technique has also been successfully applied to analyze medicinal and aromatic plants in small quantities (20,21).
As an overall result, we can deduce that the microdistillation method is an efficient and practical technique, which can be used in the analysis of volatiles of various aromatic materials in a short time at less expense. However, this work also shows that further investigations on the essential oil and the evaluation of the biological activities of Betula species should be initiated. As a renewable bioresource, Betula species can serve as a good source for natural medicines and cosmetics with a traditional background.