Characterization of Volatile Compounds in Linden Blossoms Tilia curdata Mill.

Transcription

1 FLAVOUR AND FRAGRANCE JOURNAL, VOL. 1, 5762 (1986) Characterization of Volatile Compounds in Linden Blossoms Tilia curdata Mill. J. P. Vidal and H. Richard ENSIAA, Chaire de Chimie de I AlirnentAr8mes, I avenue des Olympiades, F 91305, France 80 Compounds were identified in the LikensNickerson extracts of linden blossoms harvested near BuislesBaronnies (Dr6me, France). The composition of the essential oils extracted from the flowers and the bracts differs considerably. The essential oil derived from the flowers is characterized by a high percentage of monoterpenes (53%), and by a much lower percentage of aldehydes (12%). Whereas, oil extracted from the bracts is richer in aldehydes (25%) than in monoterpene hydrocarbons (2.04.5%), it also contains a reasonable proportion of aliphatic hydrocarbons (3.05.0%). From a liquid COz extract of the flowers, 14 different compounds were identified whose principal component was dibutyl phthalate (1 1.8%), whereas the monoterpenoids as a whole represent only 14.0% of the total extract. KEY WORDS Linden blossom aroma LikensNickerson INTRODUCTION The linden tree is a wellknown plant whose flowers are used medicinally and are reputed to have diaphoretic and diuretic properties and which has been used in the treatment of atheriosclerosis, Most of the studies to have been published on this blossom have concentrated on flavenoids, carbohydrates, * or on vitamins.13 In the only published study on the aromatic constituent^,'^ 12 varieties of linden were examined and 22 compounds were identified, amongst which 14 hydrocarbons represented between 37% and 55% of the total essential oil, depending on variety. The presence of 2phenylethanol (30.0%), geraniol (6.0%), and eugenol (0.85.0%) was also reported. MATERIALS AND METHODS Extraction of linden blossoms The linden blossoms were harvested near BuislesBaronnies (Drdme, France). Two 50 g samplesone of dried flowers, the other of dried bractswere poured into a flask with 500 ml of distilled water and then steamdistilled and simultaneously extracted by diethyl etherpentane (1:l) in a LikensNickerson apparatus for one /86/ $ by John Wiley & Sons, Ltd. Liquid COz extract hour.is The organic extract was then dried with anhydrous magnesium sulphate and then concentrated to 100 ml by removing the solvent under a stream of nitrogen. The extracts possess a pleasant linden blossomlike odour, but differ according to which part of the plant the extract comes from. 200 g of linden flowers were extracted during a three hour period at 90 bar, 24 C, with 2 kg of liquid COz, in a COz extractor similar to the one described by Vollbrecht and illustrated in Figure ml of ethanol was added to the flowers in order to improve the extraction procedure. The extract was recovered in a separator which was maintained at 40 bar, 34 C. COz was circulated continuously in the device at a flow rate of 75 ml/min. Qualitative and quantitative analyses The characterization of the extracts was carried out by a comparison of the retention times and mass spectra against those of reference samples. Compound identification by mass spectrometry was performed on a HewlettPackard Gas ChromatographMass Spectrometer (GCMS) model 5995 B equipped with a computerized data system based on a ten peak best fit. A fused silica capillary column (J&W) coated with DB5 bonded phase (film thickness: pm) was connected directly into the ionization source (70 ev). Received 27 February 1986 Accepted I I April I986

2 58 J. P. VIDAL AND H. RICHARD t 2 L 1 16 : Valves 7 : Expanslon valve HE sat exchanger P. Pump E : Extractor S Separator T Tank of C02 TC ThermOCOUple n nanometer L Liqueftsr HE HE Fig. 1. Sub critical CO2 extraction apparatus 1 pl of the LikensNickerson extracts was injected with an inlet split 1: 100. Splitless injection of C02 extracts was performed with the column maintained at room temperature during the 2 min. injection time; the temperature was rendered as low as possible by leaving the oven door open for the period of injection. The column temperature was then programmed to increase from 40 C to 220 C at a rate of 4"Cjmin. Quantitative determination was realized on a Carlo Erba Gas Chromatograph 4130 equipped with a fused silica capillary column (J&W) similar to those used for GCMS analyses. The chromatograph was connected to an integratorrecorder SAC CR 1B. Response factors were not used in calculating percentage composition from the integrator data. RESULTS AND DISCUSSIONS The compounds identified are listed in Table 1. Of the volatile compounds already reported in the literat~re,'~ only seven were to be found in our extracts: octadecane, nonadecane, eicosane, heneicosane, linalol, 2phenylethanol, and eugenol. Bernasconi and Gebistorfl4 reported 60% hydrocarbons in their linden extracts, which is very much at variance with the proportion found in our extricts (1.O5.0%). In addition they reported 28% 2phenylethanol, while we found only 0.4%. However, the same amount of eugenol was found in both studies. In the Berne linden extract, the presence in large amounts of two high molecular weight compounds, tricosane (16%) and 2phenylethyl ben zoate (4.4%), could be due to the steamdistillation times Bernasconi and Bebi~torf'~ used, which might explain why we were unable to find these compounds in our extracts. The flower extract obtained by simultaneous steam distillation extraction, whose chromatogram is illustrated in Figure 2, is characterized overall by the high content of monoterpenes (53%) and by a lower percentage of aldehydes (12%). Three compounds were found to be the major constituents of this extract: pcymene (13%), thymol (6.5%), and carvacrol (10.2%). The 'Cot extract' is characterized by the presence of 14% monoterpenes, whereas pcymene represents only 5.5%. However dibutyl phthalate (11.8%), the major compound as illustrated in Figure 3, may possibly be an artefact. The odour of this extract has a peppery note and is not reminiscent of the linden blossom odour. The extract obtained from the bracts, on the other hand, whose chromatograph is illustrated in Figure 4, is characterized by a high aldehyde content (2527%), and by a low proportion of hydrocarbons (2.04.5%). The major compound, phenylacetaldehyde, possesses a wellknown strong pungentgreen and floral odour of a hyacinth type. In a Muscat wine extract from Frontignan, Bayonove et al.," mentioned the presence of a linden blossom odour compound, tramhotrienol, that we could not identify in the samples taken from the vicinity of BuislesBaronnies. This study has revealed 82 compounds which show an important variation in the distribution according to the parts of the plant extracted and method of extraction.

3 VOLATILE COMPOUNDS IN LINDEN BLOSSOMS 59 Extraction of linden flowers by the COz method does not seem to be either suitable or significant when compared with the Likens Nickerson method, since the C02 method extract has an odour which is not at all reminiscent of what we smell when preparing a herb tea from linden blossom. Peak No Compounds 3Methylbutanal Benzene' Pent1en301 Pentanal Pentanol Chloroform* Toluene* Octane Hex an a I 2methylbutanoic acid trans2hexenal rnxylene' Nonane Heptanal athujene apinene Camphene Caproic acid Benzalde hyde HexIen301 Methyl thiohexanoatet 6methyl5hepten2one Myrcene Decane Octanal Dichlorobenzene* aterpinene pcymene Limonene Benzyl alcohol 1,8cineole Phenylacetaldehyde yterpinene cissabinene hydrate apdimethylstyrene Terpinolene Linalol Nonanal 2phenylethanol Indole 2trans6cisnonadienal trans2decenal Table 1. Volatile compounds in Linden blossoms Flowers Peak Bracts LN COz No. Compounds o Legends: compound with a percentage <0.1% * Possible artefact. t Tentative identification Metha 1 (7),2dien801 1terpinen401 pamen801 aterpineol Methyl salicylate 1.o Decanal 0.1 Safranal Verbenone Nonanoic acid 1.o Anisaldehyde 2Phenylbut2enal 0.15 Thymol 0.6 Tridecane Carvacrol 0.7 2f ram4tran.vdecadienal Decanoic acid Eugenol 0.45 Tetradecane 0.2 Vanillin ~caryophyllene aionone 0.15 Geranylacetone Pentadecane 8ionone Undecanal 0.15 BHT 4.6 cis3hexenyl benzoate 0.8 Hexadecane Dodecanal 0.1 8caryophyllene oxide cis3 hexenyl phenylacetate Heptadecane Tridecanal 0.2 Octadecane 0.1 1,2,4,6tetramethyl pentadecan2one 2.25 Diethyl phthalate. 0.2 Nonadecane Farnesylacetone Dibutyl phthalate 4.0 Heneicosane 1.o Flowers Bracts LN C f o

4 4 Y It 61 m I u Fig. 2. Chromatogram of simultaneous steam distillationextraction flower extract I 40 3? J L Fig. 3. Chromatogram of COz flower extract

5 J J Fig. 4. Ch omatogram of simultaneous distillationextraction bract extract

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