GC-MS Characterization of Acetylated β-D-glucopyranosides: Transglucosylation of Volatile Alcohols Using Almond β-glucosidase

β-D-Glucopyranosides of pentan-1-ol, (±)-pentan-2-ol, hexan-1-ol, octan-1-ol, benzyl alcohol, 2-phenylethanol, (±)-2-phenyl-propan-1-ol, 3-phenyl-propan-1-ol, geraniol and nerol were synthesized by transglucosylation of the respective alcohols with cellobiose using almond β-glucosidase. The reaction was carried out in acetonitrile with acetate buffer (vol. ratio 9:1), with the yields 14.4–45.0 %. Transglucosylation was not enantioselective. The products were characterized by GC-MS analysis of prepared tetraacetyl glucosides. Fragment ion characteristics of the aglucone moiety are present in all mass spectra, along with the fragments obtained from acetylated glucose. Acetylated glucosides are separable on HP-101 column (even diastereomeric tetraacetyl β-glucosides of enantiomeric alcohols)

GC-MS Characterization of Acetylated β-D-glucopyranosides: Transglucosylation of Volatile Alcohols Using Almond β-glucosidase

β-D-Glucopyranosides of pentan-1-ol, (±)-pentan-2-ol, hexan-1-ol, octan-1-ol, benzyl alcohol, 2-phenylethanol, (±)-2-phenyl-propan-1-ol, 3-phenyl-propan-1-ol, geraniol and nerol were synthesized by transglucosylation of the respective alcohols with cellobiose using almond β-glucosidase. The reaction was carried out in acetonitrile with acetate buffer (vol. ratio 9:1), with the yields 14.4–45.0 %. Transglucosylation was not enantioselective. The products were characterized by GC-MS analysis of prepared tetraacetyl glucosides. Fragment ion characteristics of the aglucone moiety are present in all mass spectra, along with the fragments obtained from acetylated glucose. Acetylated glucosides are separable on HP-101 column (even diastereomeric tetraacetyl β-glucosides of enantiomeric alcohols)

Composition of Free and Glycosidically Bound Volatiles of Mentha aquatica L.

Free and glycosidically bound volatiles of mentha aquatica L. were investigated. Free volatile compounds were isolated from the dried plant material by hydrodistillation and glycosides by extraction with water during hydrodistillation. Free volatile compounds (essential oil) as well as the aglycones obtained after the hydrolysis of glycosides were analyzed by gas chromatography-mass spectrometry (GC-MS). The essential oil was composed of monoterpene hydrocarbons (10.47%), sesquiterpene hydrocarbons (20.09%) and oxygen containing compounds (68.42%). The major components of the essential oil were: menthofuran (3978.08 mg kg-1), 1,8-cineole (1716.44 mg kg-1) and trans-caryophyllene (1109.20 mg kg-1). After enzymatic hydrolysis, the major volatile aglycones were: 1-octen-3-ol (30.22 mg kg-1), eugenol (10.21 mg kg-1), 2-phenylethanol (6.81 mg kg-1), 3-hexen-1-ol (5.35 mg kg-1), perilla alcohol (4.13 mg kg-1), 1-hexanol (3.58 mg kg-1), and 3-octanol (2.44 mg kg-1). Moderate similarity was found between volatile aglycones and the corresponding free volatiles in the essential oil. Acidic hydrolysis, after enzymatic hydrolysis, liberated additional amounts of aglycones. Approx. 38% of the glycosides were not hydrolyzed by the used enzyme

The Essential Oil and Glycosidically Bound Volatile Compounds of Calamintha nepeta (L.) Savi

Results of the investigation of the essential oil and glycosidically bound volatile compounds of Calamintha nepeta (L.) Savi are presented in the paper. The essential oil was isolated by hydrodistillation and glycosides were extracted with ethyl acetate. The yield of essential oil was W = 0.91%. The essential oil was fractionated on a microcolumn with solvents of different polarity. One fraction of terpene hydrocarbons and four fractions of oxygenated terpene compounds were obtained. All fractions were analyzed by gas chromatography-mass spectrometry (GC-MS) on two columns with different polarity of the stationary phases. The purpose of the fractionation was to obtain a more completely analysis. In this way, sixtyfive compounds were identified. In contrast, only twenty-four compounds were identified in the essential oil without fractionation. The main components were piperitone oxide, piperitenone oxide, limonene, caryophyllene, thymol, linalool, 3-octanol and other compounds in smaller amounts. After isolation, final purification of the glycosides by »flash« chromatography on silicagel column and enzymatic hydrolysis, the liberated aglycones were analyzed in the same way as the essential oil fractions. The content of volatile aglycones was W = 0.00081% or 8.1 mg kg-1 of the plant material. Eighteen compounds were identified. The main aglycones were eugenol, carveol, 3-octanol, 3-hexene-1-ol, 2-butanol, 2-phenylethanol, methyl salicylate, benzyl alcohol, acetophenone derivates, and others. Some of the aglycones were the same or structurally similar to the essential oil components. Glycosidically bound volatiles in this plant have not been investigated so far

Free and Bound Volatiles of Garlic Mustard (Alliaria petiolata)

Forty four volatile from Alliaria petiolata were identified after hydrodistillation in Clevengertype apparatus. Essential oils were isolated from fresh, fresh autolyzed and dry plant material. Volatile compounds were analysed by gas chromatography (GC) and gas chromatography – mass spectrometry (GC-MS). The main components were organic nitrile and sulphur compounds. They were allyl isothiocyanate (40.3–47.2 %), 3,4-epithiobutane nitrile (3.8–10.2 %), allyl nitrile (0.6–7.6 %), allyl thiocyanate (1.2–2.1 %), that are released from sinigrin glucosinolate degradation. In oils from autolyzed plant material we found diallyl disulphide (7.2 %), diallyl sulphide (0.7 %), 3-vinyl-3,4-dihydro-1,2-dithiin (0.5 %) and 2-vinyl-4H-1,3-dithiin (0.3 %) that are released by degradation of S-alke(en)yl cysteine sulphoxide. Oils, except above mentioned volatiles, contain compounds without nitrogen and sulphur: phytol (4.0–26.3 %), palmitic acid (0–14.7 %), (Z)-hex-3-en-1-ol (0.4–6.2 %), nonanal (0–3.0 %), phenylacetaldehyde (0–2.8 %), ß-ionone (0.3–1.9 %), 4-vinyl-2-methoxy-phenol (0.2–1.6 %), benzaldehyde (0.2–1.0 %). O-Glycosides with volatile aglycones were isolated and purified by »flash« chromatography. After O-glycoside hydrolysis by ß-glucosidase from almonds, fourteen bound aglycons were identified for the first time in this plant. The main aglycones were: 2-phenylethanol (20.8 %), benzyl alcohol (16.7 %), eugenol (15.7 %), (Z)-hex-3-en-1-ol (4.8 %), 3-oxo-7,8-dihydro-α-ionol (4.7 %), methyl salicylate (4.6 %) and butane-2,3-diol (4.5 %)

Essential Oil and Glycosidically Bound Volatiles of Thymus pulegioides L. growing Wild in Croatia

The present paper represents the continuation of our research of free (essential oil) and glycosidically bound volatile compounds from Croatian wild-growing aromatic plants. The essential oil and glycosidically bound volatile compounds were isolated from the fresh and dried plant material of Thymus pulegioides L. at three stages of plant development and analysed by gas chromatography-mass spectrometry (GC-MS). The most abundant constituents in essential oils were geraniol and linalool followed by thymol, g-terpinene, thymol methyl ether, borneol and geranyl acetate, all of which showed quantitative variations during the plant development stages and whether fresh or dried plants were used for essential oil isolation. After enzymatic hydrolysis of glycosidic fractions, the GC-MS analysis of volatile aglycones revealed eugenol, geraniol and 1-octen-3-ol as the main aglycones in all samples. Other important aglycones were thymoquinone, 2-phenylethanol, 3-hexenol, 3-octanol, benzyl alcohol and linalool. Quantitative variations were observed when the aglycones were analysed at three different stages of plant development. Because of the high geraniol content in the essential oils and in the aglycone fractions this Thymus pulegioides L. could be interesting as a fragrant material for perfume industry or for food flavouring

The Essential Oil and Glycosidically Bound Volatile Compounds of Calamintha nepeta (L.) Savi

Results of the investigation of the essential oil and glycosidically bound volatile compounds of Calamintha nepeta (L.) Savi are presented in the paper. The essential oil was isolated by hydrodistillation and glycosides were extracted with ethyl acetate. The yield of essential oil was W = 0.91%. The essential oil was fractionated on a microcolumn with solvents of different polarity. One fraction of terpene hydrocarbons and four fractions of oxygenated terpene compounds were obtained. All fractions were analyzed by gas chromatography-mass spectrometry (GC-MS) on two columns with different polarity of the stationary phases. The purpose of the fractionation was to obtain a more completely analysis. In this way, sixtyfive compounds were identified. In contrast, only twenty-four compounds were identified in the essential oil without fractionation. The main components were piperitone oxide, piperitenone oxide, limonene, caryophyllene, thymol, linalool, 3-octanol and other compounds in smaller amounts. After isolation, final purification of the glycosides by »flash« chromatography on silicagel column and enzymatic hydrolysis, the liberated aglycones were analyzed in the same way as the essential oil fractions. The content of volatile aglycones was W = 0.00081% or 8.1 mg kg-1 of the plant material. Eighteen compounds were identified. The main aglycones were eugenol, carveol, 3-octanol, 3-hexene-1-ol, 2-butanol, 2-phenylethanol, methyl salicylate, benzyl alcohol, acetophenone derivates, and others. Some of the aglycones were the same or structurally similar to the essential oil components. Glycosidically bound volatiles in this plant have not been investigated so far

Free and Glycosidically Bound Volatile Compounds from Cypress Cones (Cupressus Sempervirens L.)

Isolations of glycosides from fresh cypres cones, Cupressus Sempervirens L. (Cupressaceae), were performed by cold and hot ethyl acetate extraction. After enzymatic hydrolysis by means of β-glucosidase, 18 aglycones were released. The glycosidically bound volatile compounds amounted to 7-8 mg kg-1. The main aglycones were 3-hydroxybenzoic acid methyl ester (15.5%) and thymoquinone (5-isopropyl-2-methyl-1,4-benzoquinone: 3.7-9.7%). Other important aglycones were perilla alcohol (3.6-8.2%), p-cymen-8-ol (5.3-6.4%), 2-phenylethanol (2.7-6.9%) and carvacrol (2.5-6.3%). There was no similarity between the glycosidically bound aglycones and the corresponding free compounds found in the essential oil

Free and Glycosidically Bound Volatiles of Mentha citrata Ehrh.

Free and glycosidically bound volatiles of surficial parts of Mentha citrata were investigated. Free volatile compounds were isolated from dried plant material by two methods: hydrodistillation and extraction with pentane used as control. Free volatile compounds as well as the aglycones obtained after enzymatic hydrolysis of gly-cosides were analyzed by gas chromatography-mass spectrometry (GC-MS). A significant difference in qualitative and quantitative composition of volatile compounds of the essential oil and pentane extract was found. The major components of the essential oil and pentane extract were linalyl acetate (21.46%; 42.02%), linalool (13.68%; 22.66%), 1,8-cineole (12.51%; 6.40%), β-myrcene (8.10%; 2.87%), α-terpineol (7.38%; 0.73%) and geranyl acetate (8.66%; 1.76%). The major components of the volatile aglycones were 1-octen-3-ol (40.28%), eugenol (12.29%), 3-octanol (7.09%), linalool (4.59%), benzyl alcohol (3.71%), 2-phenylethanol (3.67%), 3-hexene-1-ol (2.87%) and 1-heptene-3-ol (2.88%). Compared with free volatile compounds (essential oil: 1.56%; pentane extract: 1.64% ), the glycosidically bound volatiles were present in a lower concentration, about 0.0068%

Free and Bound Sulphur Containing and Other Volatile Compounds from Evergreen Candytuft (Iberis sempervirens L.)

Volatile fractions of evergreen candytuft, Iberis sempervirens (Brassicaceae), were isolated by simultaneous hydrodistillation-extraction from fresh plant material prior and after autolysis and from dried plant material and were then analyzed using GC and GC-MS. Isothiocyanates, nitriles, aliphatic alcohols, carbonyls, fatty acids, hydrocarbons, terpene compounds, C13-norisoprenoids and phenylpropane derivatives were identified – thirty-nine components in all. Major components of all samples were: 3-butenyl isothiocyanate (17.4–63.3 %), 5-methylthiopentanonitrile (2.2–9.5 %), 4-methylthiobutanonitrile (4.8–6.9 %), allyl isothiocyanate (4.0–6.6 %), 4-methylthiobutyl isothiocyanate (2.9–6.2 %) and 3-methylthiopropyl isothiocyanate (1.3–3.4 %). Oil isolated after autolysis is more complex than the other two oils. It is composed of a large number of compounds. Some of them are identified as O-aglycones such as eugenol, (Z)-3-hexene-1-ol and 1H-indole. O-glycosides of volatile compounds were isolated from fresh plant material and purified by selective extraction and column chromatography. After hydrolysis with b-glucosidase, the liberated volatile aglycones were also analyzed by GC and GC-MS. Nineteen aglycones were identified. The main aglycones identified were: eugenol (15.2 %), 2-phenylethanol (12.9 %), 2-hydroxy-b-ionone (10.6 %), 2-tert-butyl-5-methylphenol (9.2 %) and methyl-2,5-dihydroxybenzoate (4.5 %)