Gas Chromatography-Mass Spectrometry Analysis of Volatile Organic Compounds from Three Endemic Iris Taxa: Headspace Solid-Phase Microextraction vs. Hydrodistillation.

Iris taxa are sources of valuable essential oils obtained from aged rhizomes used by various industries, including pharmacy, cosmetic, perfume, and food industry, in which irones are the most important aroma components. In this study, volatile organic compounds (VOCs) obtained from dried rhizomes of three endemics from Croatia, Iris pseudopallida, I. illyrica, and I. adriatica, were studied. The VOCs were isolated by three different methods: headspace solid-phase microextraction (HS-SPME) using divinylbenzene/carboxene/polydimethylsiloxane (DVB/CAR/PDMS) fiber or polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber, and hydrodistillation (HD). The samples were analyzed by gas chromatography-mass spectrometry (GC-MS). In five out of six samples, the main compounds detected by HS-SPME were perilla aldehyde, butan-2,3-diol, acetic acid, 2-phenylethanol, benzyl alcohol, hexanal, and nonanal, while 6-methylhept-5-en-2-one, trans-caryophyllene, and ethanol were common for all studied samples. The former VOCs were absent from the oldest, irone-rich I. pseudopallida sample, mainly characterized by cis-α-irone (43.74-45.76%). When using HD, its content was reduced (24.70%), while docosane prevailed (45.79%). HD yielded predominantly fatty acids, including myristic, common for all studied taxa (4.20-97.01%), and linoleic (40.69%) and palmitic (35.48%) as the major VOCs of I. adriatica EO. The performed GC-MS analyses of EOs, in combination with HS-SPME/GC-MS, proved to be useful for gaining a better insight into Iris VOCs.

Screening of Satureja subspicata Vis. Honey by HPLC-DAD, GC-FID/MS and UV/VIS: Prephenate Derivatives as Biomarkers.

The samples of Satureja subspicata Vis. honey were confirmed to be unifloral by melissopalynological analysis with the characteristic pollen share from 36% to 71%. Bioprospecting of the samples was performed by HPLC-DAD, GC-FID/MS, and UV/VIS. Prephenate derivatives were shown to be dominant by the HPLC-DAD analysis, particularly phenylalanine (167.8 mg/kg) and methyl syringate (MSYR, 114.1 mg/kg), followed by tyrosine and benzoic acid. Higher amounts of MSYR (3-4 times) can be pointed out for distinguishing S. subspicata Vis. honey from other Satureja spp. honey types. GC-FID/MS analysis of ultrasonic solvent extracts of the samples revealed MSYR (46.68%, solvent pentane/Et2O 1:2 (v/v); 52.98%, solvent CH2Cl2) and minor abundance of other volatile prephenate derivatives, as well as higher aliphatic compounds characteristic of the comb environment. Two combined extracts (according to the solvents) of all samples were evaluated for their antioxidant properties by FRAP and DPPH assay; the combined extracts demonstrated higher activity (at lower concentrations) in comparison with the average honey sample. UV/VIS analysis of the samples was applied for determination of CIE Lab colour coordinates, total phenolics (425.38 mg GAE/kg), and antioxidant properties (4.26 mmol Fe(2+)/kg (FRAP assay) and 0.8 mmol TEAC/kg (DDPH assay)).

Glucosinolate degradation products of Aurinia leucadea (Guss.) K.Koch and Lepidium draba L. from Croatia.

Two wild-growing Brassicaceae plants of Croatian origin, Aurinia leucadea (Guss.) K. Koch and Lepidium draba L., were investigated to uncover glucosinolates via GC/MS analysis of their degradation products. The main constituents of Aurinia leucadea (Guss.) K.Koch distillate were hex-5-enenitrile (28.8%) and but-3-enyl isothiocyanate (18.8%), while 4,5-epithiopentanenitrile (50%) and 5,6-epithiohexanenitrile (18.5%) were the main volatile compounds in autolysate. 4-(Methylsulfanyl)butyl isothiocyanate (96.4%) constituted almost the entire Lepidium draba L. distillate, while the autolysate was characterized by 4-(methylsulfinyl)butyl isothiocyanate (57.3%). So, regarding the glucosinolate degradation products, the main glucosinolates of A. leucadea were glucobrassicanapin and gluconapin, and of L. draba glucoerucin and glucoraphanin.

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 CH(2) Cl(2) 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.

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 CH(2) Cl(2) 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.

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-alpha-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-beta-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 microg/ml using the disc diffusion method.

Glucosinolate Profiling of Calepina irregularis.

Three different types of extracts of volatile isolates from aerial parts of Calepina irregularis (Asso) Thell. were investigated to uncover glucosinolates using indirect methods consisting of either non-enzymatic (thermal degradation) or enzymatic (with exogenous and endogenous myrosinase) hydrolysis, followed by GC-FID/MS analysis of the volatile isolates. The identification of volatile glucosinolate degradation products isolated from C. irregularis indirectly revealed the presence of seven glucosinolates, namely glucoiberverin, glucoiberin, glucocheirolin, glucolepidiin, sinigrin, glucoerucin and glucotropacolin. Quantitatively the most important compound in the distillate (sample obtained by thermal degradation) was 3-(methylthio)propyl isothiocyanate (95 61/), the degradation product of glucoiberverin, which constituted almost the entire sample. Tw6 isothiocyanates, 3-(methylthio)propyl isothiocyanate (57.8%) and 3 (methylsulfinyl)propyl isothiocyanate (16.7%), originating from degradation of glucoiberverin and glucoiberin, respectively, were the most abundant compounds identified in the hydrolysate (sample obtained by exogenous myrosinase hydrolysis). Some isothiocyanates, 3-(methylthio)propyl isothiocyanate and 3-(methylsulfinyl)propyl isothiocyanate, were present in almost the same percentages (41.0% and 40.0%, respectively), in the autolysate (endogenous myrosinase hydrolysis).

Comparison of different methodologies for detailed screening of Taraxacum officinale honey volatiles.

Headspace solid-phase microextraction (HS-SPME), ultrasonic solvent extraction (USE) and solid phase extraction (SPE), followed by GC-FID/MS were used for screening of dandelion (Taraxacum officinale Weber) honey headspace, volatiles and semi-volatiles. The obtained results constitute a breakthrough towards screening of dandelion honey since dominant compounds identified in the extracts were not previously reported for this honey type. Nitriles dominated in the headspace, particularly 3-methylpentanenitrile (up to 29.9%) and phenylacetonitrile (up to 20.9%). Lower methyl branched aliphatic acids and norisoprenoids were relevant minor constituents of the headspace. The extracts contained phenylacetic acid (up to 24.0%) and dehydrovomifoliol (up to 19.3%) as predominant compounds, while 3-methylpentanenitrile and phenylacetonitrile were detected in the extracts in minor abundance. Dehydrovomifoliol can be considered more characteristic for dandelion honey in distinction from phenylacetic acid. Low molecular aliphatic acids, benzene derivatives and an array of higher aliphatic compounds were also found in the extracts. The results of SPE/GC-FID/MS were very similar to USE/GC-FID/MS with the solvent dichloromethane. The use of all applied methodologies was relevant for the comprehensive chemical fingerprinting of dandelion honey volatiles.

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%) a nd gamma-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 beta-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 gamma-terpinene, alpha-terpinene, p-cymene and terpinolene which previously were identified as potential antioxidants.

Antibacterial activity of Achillea clavennae essential oil against respiratory tract pathogens.

The essential oil of Achillea clavennae was investigated for its antibacterial activity against some respiratory tract pathogens. Maximum activity was observed against Klebsiella pneumoniae and penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae. The oil also exhibited strong activity against Gram (-) Haemophilus influenzae and Pseudomonas aeruginosa. Gram (+) Streptococcus pyogenes was the most resistant to the oil.

Chemical composition and antioxidant test of free and glycosidically bound volatile compounds of savory (Satureja montana L. subsp. montana) from Croatia.

The evaluation of antioxidant power of glycosidically bound volatile aglycones from savory shows that these compounds possess antioxidative activity comparable to that of the essential oil, but less effective compared to the well-known antioxidant butylated hydroxytoluene (BHT) and alpha-tocopherol. Thus, since the glycosides are able to release their aglycones by enzymatic hydrolysis, they could be considered as possible precursors of antioxidant substances in savory.

Composition and antimicrobial activity of Achillea clavennae L. essential oil.

The volatile constituents of Achillea clavennae L. (Asteraceae), rare plant of Europe, have been analysed using GC/MS. Twenty- five components making up 81.6% of the oil were characterized with camphor (29.5%), myrcene (5.5%), 1,8-cineole (5.3%), beta-caryophyllene (5.1%) and linalool (4.9%) being the major constituents. The essential oil was evaluated for antibacterial and antifungal activities. The screening of the antimicrobial activity of essential oil was conducted by a disc diffusion test against Gram-positive (Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Streptococcus faecalis), Gram-negative (Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis) and fungal organisms (Aspergillus niger, Aspergillus fumigatus, Candida albicans). The activity was more pronounced against Gram-negative and fungal organisms than against Gram-positive bacteria. A. clavennae oil was found to possess antimicrobial activity against Klebsiella pneumoniae, Pseudomonas aeruginosa and all fungal organisms.