Josip Mastelić

Chemical composition and antioxidant effect of glycosidically bound volatile compounds from oregano (Origanum vulgare L. ssp. hirtum).

Abstract The present work examines the content and chemical composition of the glycosidically bound volatiles from oregano as well as their antioxidative properties. The glycosidically bound volatiles amounted to 20 mg kg−1 in dried leaves and flowers of oregano. Fourteen volatile aglycones were identified with thymoquinone as the major component. Other important aglycones were benzyl alcohol, eugenol, 2-phenyl-ethanol, thymol, 3-hexen-1-ol and carvacrol. It was found that all of the aglycones have an antioxidant effect when tested by measuring peroxide values of lard stored at 60°C. These results were compared to the antioxidative activity of oregano essential oil, pure thymol, thymoquinone and also to α-tocoferol which is well known among natural antioxidant compounds.

Gas chromatography-mass spectrometry analysis of free and glycoconjugated aroma compounds of seasonally collected Satureja montana L.

The present work examines the content and composition of glycoconjugated and free volatile aroma compounds in the plant material of savory, depending on the stage of plant development. Free volatile compounds (essential oil) as well as volatile aglycones obtained after the enzymatic hydrolysis of isolated glycosides were analyzed by coupled gas chromatography–mass spectrometry (GC–MS). Thirty-six compounds were identified in the essential oil and 17 compounds among the volatile aglycones. The main components of essential oil (yield 0.80–1.46% w/w, SD=0.02–0.03) were thymol (30.88–46.02%, SD=0.40–0.45), p-cymene (7.10–13.48%, SD=0.19–0.27), γ-terpinene (7.57–9.74%, SD=0.19–0.23) and carvacrol (3.81–6.86%, SD=0.05–0.07). The main aglycones (yield 58.4–95.6 mg kg−1, SD=1.5–3.0) were: thymoquinone (27.55–32.93%, SD=0.38–0.40), eugenol (8.35–19.44%, SD=0.06–0.23), cis-3-hexene-1-ol (2.38–9.73%, SD=0.04–0.22) and thymol (4.07–7.81%, SD=0.05–0.06). Other aglycones in lower percentages were p-cymen-8-ol, α-terpineol, geraniol, benzyl alcohol, 2-methoxy-4-ethyl-6-methylphenol, 1-octen-3-ol, methyl salicylate, 3,5,5-trimethyl-4-(3-hydroxy-1-buthenyl)-2-cyclohexene-1-one, carvacrol and other compounds. The results show moderate similarity in the chemical composition of oil and volatile aglycones. In the aglycones fraction, the contents of thymoquinone and thymol decreased with maturation of the plant, and contents of eugenol, nerol, geraniol, increased in the same time. This is mainly in agreement with seasonal variations of the main oil components.

Composition and Antimicrobial Activity of Helichrysum italicum Essential Oil and Its Terpene and Terpenoid Fractions

The essential oil of Helichrysum italicum (Roth) G. Don from Croatia has been fractionated into terpene and terpenoid fractions and analyzed using GC/MS. Fifty-two compounds were identified. The main hydrocarbons of the oil were α-pinene (10.2%), α-cedrene (9.6%) aromadendrene (4.4%), β-caryophyllene (4.2%), and limonene (3.8%), while the main oxygen-containing compounds were neryl acetate (11.5%), 2-methylcyclohexyl pentanoate (8.3%), 2-methylcyclohexyl octanoate (4.8%), and geranyl acetate (4.7%). The essential oil and its terpene and terpenoid fractions were evaluated for antibacterial and antifungal activities. The screening of antimicrobial activity was conducted by a disc diffusion test and the minimum inhibitory concentration was determined against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. The essential oil and its terpenoid fraction exhibited higher antimicrobial activity with respect to the terpene fraction. The antimicrobial activities of the oil and its terpenoid fraction were more pronounced against Staphylococcus aureus and Candida albicans.

Volatile compounds from leaf-buds of Populus nigra L. (Salicaceae)

Volatile components from fresh and air-dried leaf-buds of Populus nigra L. (Salicaceae) were isolated by Likens-Nickerson apparatus and analyzed using GC/MS. Forty-eight components (ca. 95% of the total isolate) were identified among black poplar bud volatiles. Sesquiterpene alcohols beta-eudesmol and alpha-eudesmol represented 26.3-28.7% of the oil. Other major sesquiterpene compounds were gamma-selinene (7.6-8.8%), delta-cadinene (7.8-8.6%), alpha-elemene (3.3-5.2%) and gamma-cadinene (3.9-4.2%). Hemiterpenes were also identified (2.2-7.6%). Monoterpenes were present in low percentages (1.6-5.7%). Aliphatic and aromatic alcohols, carbonyl compounds and aliphatic acids were identified among non-terpene volatiles (9.8-13.5%). The fresh buds contained 0.27% and dried 0.12% essential oil. Air-drying moderately effected the volatiles qualitative and quantitative composition.

Free and Glycosidically Bound Volatiles of Mentha longifolia Growing in Croatia

The glycosides of volatile compounds and the essential oil were isolated from wild Mentha longifolia. After the enzymatic hydrolysis of glycosides, fourteen volatile aglycones were identified by GC/MS. The main aglycones were eugenol, 2-phenylethanol, benzyl alcohol, lavandulol, trans- and cis-carveol, 3-octanol, and 3-hexen-1-ol. The content of aglycones was 40.85 mg kg-1 of dried plant material. The main components of the essential oil (yield 0.93 w/w) were carvone, piperitenone oxide, limonene, and β-caryophyllene. Eugenol, carveol, 3-octanol, and α-terpineol were identified in the aglycones and in the essential oil.

Phytochemical Analysis and Antimicrobial Activity of Cardaria draba (L.) Desv. Volatiles

Two different volatile isolates from the aerial parts of Cardaria draba (L.) Desv., obtained either by hydrodistillation (Extract I) or by CH2Cl2 extraction subsequent to hydrolysis by exogenous myrosinase (Extract II), were characterized by GC‐FID and GC/MS analyses. The main volatiles obtained by hydrodistillation, i.e., 4‐(methylsulfanyl)butyl isothiocyanate (1; 28.0%) and 5‐(methylsulfanyl)pentanenitrile (2; 13.8%), originated from the degradation of glucoerucin. In Extract I, also volatiles without sulfur and/or nitrogen were identified. These were mostly hexadecanoic acid (10.8%), phytol (10.2%), dibutyl phthalate (4.5%), and some other compounds in smaller percentages. Extract II contained mostly glucosinolate degradation products. They originated from glucoraphanin, viz., 4‐(methylsulfinyl)butyl isothiocyanate (3; 69.2%) and 5‐(methylsulfinyl)pentanenitrile (4; 4.5%), glucosinalbin, viz., 2‐(4‐hydroxyphenyl)acetonitrile (5; 7.2%), and glucoerysolin, viz., 4‐(methylsulfonyl)butyl isothiocyanate (6; 5.0%). Moreover, the volatile samples were evaluated for their antimicrobial activity using the disc‐diffusion method and determining minimum inhibitory concentrations (MIC). All volatile isolates expressed a wide range of growth inhibition activity against both Gram‐positive and Gram‐negative bacteria and fungi. The MIC values varied between 4 and 128 μg/ml.

The effect of air-drying on glycosidically bound volatiles from seasonally collected origano (Origanum vulgare ssp. hirtum) from Croatia

The glycosidically bound volatiles were isolated from fresh and airdried origano by exhaustive percolation with ethyl acetate. After the purification of glycosidic fraction, the enzymatic hydrolysis with beta-glucosidase was performed. The obtained aglycones were analysed by GC-MS. Eighteen compounds were identified. The seasonal variations of main aglycone contents from the fresh plant material were: thymoquinone (3.10-6.18 mg/kg), benzyl alcohol (1.33-3.62 mg/kg), 3,5,5-trimethyl-4-(3-hydroxy-1-buthenyl)-2-cyclohexen-1-on (0.51-3.35 mg/kg), 2-phenyl ethanol (0.42-2.98 mg/kg), eugenol (0.93-2.55 mg/kg), thymol (0.70-1.40 mg/kg) and carvacrol (0.88-1.40 mg/kg). The season of collecting influenced the content and composition of the glycosidically bound volatiles of origano. Air-drying effected mostly the yield of these compounds.

Hydrodistillation-adsorption method for the isolation of water-soluble, non-soluble and high volatile compounds from plant materials.

Proposed method of hydrodistillation-adsorption (HDA) on activated carbon and hydrodistillation (HD) with solvent trap were compared for the isolation of water-soluble, non-soluble and high volatile compounds, such as acids, monoterpenes, isothiocyanates and others from carob (Certonia siliqua L.), rosemary (Rosmarinus officinalis L.) and rocket (Eruca sativa L.). Isolated volatiles were analyzed by GC and GC/MS. The main advantages of HDA method over ubiquitous HD method were higher yields of volatile compounds and their simultaneous separation in three fractions that enabled more detail analyses. This method is particularly suitable for the isolation and analysis of the plant volatiles with high amounts of water-soluble compounds. In distinction from previously published adsorption of remaining volatile compounds from distillation water on activated carbon, this method offers simultaneous hydrodistillation and adsorption in the same apparatus.

Contribution to the Analysis of the Essential Oil of Helichrysum italicum (Roth) G. Don. - Determination of Ester Bonded Acids and Phenols

The essential oil of Helichrysum italicum (Roth) G. Don (everlasting or Immortelle essential oil) was isolated by hydrodistillation and analysed by GC and GC-MS. Forty four compounds were identified. The main components were α-pinene (12.8%), 2-methyl-cyclohexyl pentanoate (11.1 %), neryl acetate (10.4%), 1,7-di-epi-α-cedrene (6.8%) and other compounds. The oil was fractionated and ester-containing fraction was hydrolysed with KOH/H2SO4. The liberated volatiles were analysed by GC and GC-MS: three phenols and twenty seven volatile carboxylic acids were identified [70% low fatty acids (C2-C5), 15% C10-C12 acids and 15% other acids]. The main acids were acetic acid (24.3%) propanoic acid (17.2%), 2-methylpropanoic acid (11.4%), dodecanoic acid (8.7%), 2-methylbutanoic acid (8.3%), (Z)-2-methylbutenoic acid (5.1%) and decanoic acid (4.6%). With respect to the identified bonded carboxylic acids, the minimal number of esters in the oil was twenty seven, but their overall quantity was probably larger due to different possible combinations of alcohols with acids to form esters. On the other hand, only six main esters were identified in the oil before fractionation and hydrolysis.

Essential oil and glycosidically bound volatiles of Origanum vulgare L. ssp. hirtum (Link) Ietswaart

The glycosidically bound volatiles were isolated from dried plant material by percolation with ethyl acetate and by extraction with water during hydrodistillation of essential oil. Fifteen volatile aglycones were identified by gas chromatography-mass spectrometry (GC-MS) on two columns with different polarity of the stationary phases. The main aglycones were: thymoquinone, benzyl alcohol, thymol, 2-phenylethanol, carvacrol and 1-octen-3-ol. The content of aglycones was 19 and 21 mg kg−1 with respect to the method of isolation. The chemical composition of aglycones was compared with the chemical composition of essential oil, which consisted mainly of thymol and carvacrol. After the hydrolysis of glycosides, D-(+)-glucose and unknown disaccharide were identified. The hydrolysis of disaccharide, D-(+)-glucose and D-(+)-galactose were detected by TLC and GC-MS as trimethylsilylethers. Copyright