Ani Radonić

Chemical Composition and In Vitro Evaluation of Antioxidant Effect of Free Volatile Compounds From Satureja montana L

As a part of an investigation of natural antioxidants from Dalmatian aromatic plants, in this paper we report a study of the antioxidant activity related to the chemical composition of savory free volatile compounds. Twenty-one compounds were identified in the essential oil without fractionation, representing 97.4% of the total oil. The major compound was phenolic monoterpene thymol (45.2%). Other important compounds were monoterpenic hydrocarbons p-cymene (6.4%) and γ-terpinene (5.9%) and oxygen-containing compounds carvacrol methyl ether (5.8%), thymol methyl ether (5.1%), carvacrol (5.3%), geraniol (5.0%) and borneol (3.9%). The evaluation of antioxidant power was performed in vitro by the β-carotene bleaching and thiobarbituric acid (TBA) methods. As determined with both methods, the total savory essential oil as well as different fractions or pure constituents containing hydroxyl group exhibited relatively strong antioxidant effect. The hydrocarbons, when isolated as CH fraction, showed the poorest effectiveness in spite the fact that this fraction contained γ-terpinene, α-terpinene, p-cymene and terpinolene which previously were identified as potential antioxidants.

Comparative Study of Leaf, Fruit and Flower Essential Oils of Croatian Myrtus communis L. During a One Year Vegetative Cycle

Abstract The content and composition variations of the leaf, flower and fruit oils of Myrtus communis L. were studied during a one-year vegetative cycle. The plant material was harvested from the ecologically pure area on the island of Vis (Croatia). Yield and composition of myrtle oils depended on collected plant parts and on the period of harvest. Myrtenyl acetate (13.5–30.7%), 1, 8-cineole + limonene (12.6–29.8%), linalool (10.8–18.3%) and α-pinene (6.6–16.4%) were five predominant terpenoid compounds in myrtle leaf oils. These compounds were also detected in the flower and fruit oils, but in different proportions. The fruit and flower oils always contained less linalool than leaf oils. During the collecting period the oil yields (w/w) varied as follows: leaf oils (0.19–0.37%), flower oils (0.21–0.26%) and fruit oils (0.03–0.13%).

Gas chromatography mass spectral analysis of free and glycosidically bound volatile compounds from Juniperus oxycedrus L. growing wild in Croatia.

The essential oils in fresh needles and green and mature berries of Juniperus oxycedrus L. (Cupressaceae) were analyzed by GC–MS. A total of 36 compounds were identified from needles, representing 94.91% of the total oil. 15 compounds were identified in the green berry oil and 22 in the mature berry oil, which accounted for 94.33 and 90.94% of the total oil composition. The major component was α-pinene. The glycosidically bound volatile compounds amounted to 21 mg kg−1 in needles and 4 mg kg−1 from green berries. Only traces of aglycones were identified in mature berries. Sixteen volatile aglycones were identified in needle sample with 2-hydroxy-5-methylacetophenone as major component. A total of nine aglycones were identified in green berries. The major aglycones were 3-phenyl-2-propen-1-ol and myrtenol. There was no similarity between the glycosidically bound aglycones and the corresponding free compounds found in the essential oil.

Comparison of the Volatile Constituents of Propolis Gathered in Different Regions of Croatia

Volatile compounds isolated from propolis, collected in two different regions of Croatia, were analysed by GC-MS, and differed qualitatively and quantitatively. The major volatile components of Dalmatian propolis identified were terpenes (30%), while benzyl alcohol, benzoic acid and benzyl benzoate were predominant (49%) in propolis from Slavonia. The compounds α-pinene, β-pinene, γ-terpinene, α-muurolene, γ-cadinene and δ-cadinene have not previously been identified as components of propolis.

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.

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.

Seasonal Variation in Essential Oil Compositions of Cupressus sempervirens L.

Abstract The essential oils from fresh leaves of Cupressus sempervirens L. were subjected to GC/MS analysis in order to determine seasonal variations in their chemical composition. The plant material was collected within 12 months (1999) in the central part of Dalmatia (Croatia). The qualitative composition of the components appeared to be constant. However there were notable differences in the amounts of several compounds. The main component was α-pinene (28.4–79.2%). Other important components were γ-3-carene (9.1–32.6%), α-cedrol (1.2–12.9%), limonene (1.4–8.7%), terpinolene (0.6–7.0%) and α-terpinyl acetate (0.8–4.5%).

Hedge Mustard (Sisymbrium officinale): Chemical Diversity of Volatiles and Their Antimicrobial Activity

Volatile compounds of hedge mustard (Sysimbrium officinale) have been investigated for the first time. Forthy‐two compounds were identified after hydrodistillation (without or upon autolysis) after gas chromatography and gas chromatography/mass spectrometry analyses. In addition, after decoction and hydrolysis of O‐glycosides, 18 volatile O‐aglycones were identified. In general, the main volatiles found in hydrodistillates were: isopropyl isothiocyanate (27.6–48.9%), 2‐methylpropanenitrile (0.5–18.8%), (Z)‐hex‐3‐en‐1‐ol (0.5–18.0%), sec‐butyl isothiocyanate (4.9–9.4%), (E)‐hex‐2‐enal (3.5–8.6%), (Z)‐hex‐2‐en‐1‐ol (0.3–8.4%), octanoic (0.5–8.6%) and dodecanoic acid (0–5.0%), 2‐methylbutanenitrile (0–4.6%), dibutyl phthalate (0–4.5%), and ethyl linolenate (0–3.6%). The main volatile O‐aglycones were: 2‐phenylethyl alcohol (21.5%), 6,7‐dehydro‐7,8‐dihydro‐3‐oxo‐α‐ionol (9.3%), eugenol (8.3%), benzyl alcohol (7.0%), ethyl vanillate (5.2%), 6‐(tert‐butyl)‐5‐methylphenol (5.1%), vanillin acetone (4.7%), ethyl 4‐hydroxybenzoate (4.3%), and 2‐hydroxy‐β‐ionone (3.8%). All hydrodistillates exhibited great potential of antibacterial activity against five Gram‐positive bacteria, nine ampicillin‐resistant Gram‐negative bacteria, and four fungi at a concentration of 500 μg/ml using the disc diffusion method.

Glucosinolate Profiling and Antimicrobial Screening of Aurinia leucadea (Brassicaceae)

Glucosinolates (GLs) were characterized in various aerial parts (stems, leaves, and flowers) of Aurinia leucadea (Guss.) C. Koch and quantified according to the ISO 9167‐1 official method based on the HPLC analysis of desulfoglucosinolates. Eight GLs, i.e., glucoraphanin (GRA), glucoalyssin (GAL; 1), gluconapin (GNA; 2), glucocochlearin (GCC), glucobrassicanapin (GBN; 3), glucotropaeolin (GTL), glucoerucin (GER), and glucoberteroin (GBE) were identified. The total GL contents were 57.1, 37.8, and 81.3 μmol/g dry weight in the stems, leaves, and flowers, respectively. The major GL detected in all parts of the plant was 2, followed by 1 and 3. GC/MS Analysis of the volatile fractions extracted from the aerial parts of fresh plant material either by hydrodistillation or CH2Cl2 extraction showed that these fractions mostly contained isothiocyanates (ITCs). The main ITCs were but‐3‐enyl‐ (55.6–71.8%), pent‐4‐enyl‐ (7.6–15.3%), and 5‐(methylsulfinyl)pentyl ITC (0–9.5%), originating from the corresponding GLs 2, 3, and 1, respectively. The antimicrobial activity of the volatile samples was investigated by determining inhibition zones with the disk‐diffusion method and minimal inhibitory concentrations (MIC) with the microdilution method. They were found to inhibit a wide range of bacteria and fungi, with MIC values of 2.0–32.0 μg/ml, indicating their promising antimicrobial potential, especially against the fungi Candida albicans and Rhizopus stolonifer as well as against the clinically important pathogen Pseudomonas aeruginosa.

Red clover (Trifolium pratense L.) honey: volatiles chemical-profiling and unlocking antioxidant and anticorrosion capacity

Headspace solid-phase micro-extraction (HS-SPME) and ultrasonic solvent extraction (USE) were used for red clover honey volatiles extraction. The extracts were analysed using gas chromatography and mass spectrometry (GC-MS). Lilac aldehyde isomers dominated in the headspace (individual range from 7.6 % to 21.4 %) followed by phenylacetaldehyde (10.1–31.2 %) and benzaldehyde (7.0–15.7 %). Higher aliphatic alcohols and hydrocarbons were the predominant constituents of the honey extracts. The honey and its extracts exhibited rather weak anti-radical activity (DPPH assay) and total antioxidant activity (FRAP assay). On the other hand, the honey’s inhibitive properties towards the corrosion of AA 2017A alloy in NaCl solution (potentiodynamic polarisation and potentiostatic pulse measurements) revealed the honey to be a very good anodic inhibitor (efficiency up to 76 %) while the honey extracts (USE) showed better inhibition efficacy.