Synthesis of Small Libraries of Natural Products: Part II: Identification of a New Natural Product from the Essential Oil of Pleurospermum austriacum (L.) Hoffm. (Apiaceae).

Herein, comprehensive data of NMR, MS, IR, and gas chromatography (RI) obtained by GC-MS on commonly used capillary columns of different polarity (non-polar DB-5MS and polar HP-Innowax) of a series of esters of all constitutional isomers of hexanoic acid with a homologous series of ω-phenylalkan-1-ols (phenylmethanol, 2-phenylethanol, 3-phenylpropan-1-ol, 4-phenylbutan-1-ol, and 5-phenylpentan-1-ol) and phenol, in total 48 chemical entities, were collected. The created synthetic library allowed the identification of a new constituent of the P. austriacum essential oil (3-phenylpropyl 2-methylpentanoate). The accumulated spectral and chromatographical data, as well as the established correlation between RI values and structures of regioisomeric hexanoates, provide (phyto)chemists with a tool that will make future identification of related natural compounds a straightforward task.

A series of esters of diastereomeric menthols: Comprehensive mass spectral libraries and gas chromatographic data.

A comprehensive data collection of mass spectral and gas chromatographic data of a series of esters of diastereomeric menthols (menthol, isomenthol, neomenthol, and neoisomenthol), in total 150 chemical entities, obtained by GC-MS on commonly used capillary columns of different polarity (non-polar HP-5MS and polar HP-Innowax), was created. Also, MS libraries containing electron ionization MS recorded on single quadrupole as well as on quadrupole ion-trap mass detectors together with the RIs on non-polar and polar columns were compiled (available as supplementary materials). The results point out to frequent misidentification of neoisomenthyl acetate as isomenthyl acetate in the literature, and the means of how to resolve this issue was suggested. The outcomes of this study provide chemists and food technologists with a useful tool in the field of food analysis of compounds with important food aroma properties.

New Natural Products from Asphodelus albus MILL. Essential Oil.

A detailed chemical analysis of the essential oil of Asphodelus albus roots performed in this work, in combination with a chemical synthesis approach - the synthesis of selected compounds and their detailed spectral analysis - has led to the identification of a series of new natural products, the esters of furan-3-ylmethanol: furan-3-ylmethyl 2-methylpropanoate, furan-3-ylmethyl butanoate, furan-3-ylmethyl 2-methylbutanoate, furan-3-ylmethyl 3-methylbutanoate, furan-3-ylmethyl pentanoate, furan-3-ylmethyl 4-methylpentanoate, and furan-3-ylmethyl hexanoate.

Spasmolytic, antimicrobial and cytotoxic activities of 5-phenylpentyl isothiocyanate, a new glucosinolate autolysis product from horseradish (Armoracia rusticana P. Gaertn., B. Mey. & Scherb., Brassicaceae).

Detailed analyses of horseradish autolysates led to the identification of a new natural product, 5-phenylpentyl isothiocyanate (PhPeITC). The structural assignment was corroborated by synthesis, and the identity unequivocally established by spectral means. The occurrence of PhPeITC is the first direct proof of the existence of a 5-phenylpentyl glucosinolate in the aerial parts of this species as one of the possible "mustard oil" precursors. To verify its possible contribution to the horseradish functional food status, horseradish above- and underground autolysates, together with five ω-phenylalkyl isothiocyanates were tested for their spasmolytic, cytotoxic and antimicrobial activities. Specifically, the cytotoxic effect on Caco-2, HeLa (cancer) and MDCK (non-cancer) cell lines was established. Additionally, the five tested ITCs exerted significant spasmolytic activity (on rat distal colon), with PhPeITC being almost 100 times more potent than papaverine. A non-selective antimicrobial activity of all ITCs was revealed in the case of 6 bacterial and 2 fungal strains.

Chemical Composition of the Essential Oil and Diethyl Ether Extract of Trinia glauca (L.) Dumort. (Apiaceae) and the Chemotaxonomic Significance of 5-O-Methylvisamminol.

Analyses by GC, GC/MS, and NMR spectroscopy (1D- and 2D-experiments) of the essential oil and Et2O extract of Trinia glauca (L.) Dumort. (Apiaceae) aerial parts allowed a successful identification of 220 constituents, in total. The major identified compounds of the essential oil were (Z)-falcarinol (10.6%), bicyclogermacrene (8.0%), germacrene D (7.4%), δ-cadinene (4.3%), and ß-caryophyllene (3.2%), whereas (Z)-falcarinol (47.2%), nonacosane (7.4%), and 5-O-methylvisamminol (4.0%) were the dominant constituents of the extract of T. glauca. One significant difference between the compositions of the herein and the previously analyzed T. glauca essential oils (only two reports) was noted. (Z)-Falcarinol was the major constituent in our case, whereas germacrene D (14.4 and 19.6%) was the major component of the previously studied oils. Possible explanations for this discrepancy were discussed. 5-O-Methylvisamminol, a (furo)chromone identified in the extract of T. glauca, has a limited occurrence in the plant kingdom and is a possible excellent chemotaxonomic marker (family and/or subfamily level) for Apiaceae.

ANTIMICROBIAL AND ANTIBIOFILM EFFECTS OF EXTRACTS FROM TRAPA NATANS L., EVALUATION OF TOTAL PHENOLIC AND FLAVONOID CONTENTS AND GC-MS ANALYSIS.

Research conducted in this study shows the applied in vitro antimicrobial and antibiofilm activity of the four extracts isolated from Trapa natans L. leaves. In this study, different methods were used (microdilution, tissue culture plate, different colorimetric methods, GC-FID and GC-MS analysis). While the water extract didn't show antibacterial activity, the acetone extract showed the strongest one. The same activity in the case of Pseudomonas aeruginosa (MIC was 313 µg/mL) was better than the activity of controls and it matched with antibiofilm activity. The effect of extracts was better on G+ bacteria (MICs were <78-625 µg/mL). For ethanol and ethyl acetate extracts all BIC values were better than MICs. Extracts showed a significant effect on Aspergillus restrictus (MICs were < 78/156 µg/mL). The GC and GC-MS analysis of the ethyl acetate extract revealed the identification of 22 compounds with (all E)-squalene (20.2%), n-alkanes and norlignan hinokiresinol among the most abundant ones. This is the first time that T. natans was studied using these methods.

Phytomedical investigation of Najas minor All. in the view of the chemical constituents.

Plants are an abundant natural source of effective antibiotic compounds. Phytomedical investigations of certain plants haven't still been conducted. One of them is Najas minor (N. minor), an aquatic plant with confirmed allelopathy. Research conducted in this study showed the influence of water and ethyl acetate extracts of N. minor on microorganisms, in the view of chemical profiling of volatile constituents and the concentrations of total phenols, flavonoids and tannins. Antimicrobial activity was defined by determining minimum inhibitory and minimum microbicidal concentrations using microdilution method. Influence on bacterial biofilm formation was performed by tissue culture plate method. The total phenolics, flavonoids and condensed tannins were determined by Folin-Ciocalteu, aluminum chloride and butanol-HCl colorimetric methods. Chemical profiling of volatile constituents was investigated by GC and GC-MS. Water extract didn't have antimicrobial activity below 5000 µg/mL. Ethyl acetate extract has shown strong antimicrobial activity on G+ bacteria - Staphylococcus aureus PMFKGB12 and Bacillus subtilis (MIC < 78.13 µg/mL). The best antibiofilm activity was obtained on Escherichia coli ATCC25922 (BIC50 at 719 µg/mL). Water extract had higher yield. Ethyl acetate extract had a significantly greater amount of total phenolics, flavonoids and tannins. As major constituent hexahydrofarnesyl acetone was identified. The ethyl acetate extract effected only G+ bacteria, but the biofilm formation of G-bacteria was suppressed. There was a connection between those in vivo and in vitro effects against pathogenic bacterial biofilm formation. All of this points to a so far unexplored potential of N. minor.

Essential oils and diethyl ether extracts of Serbian Xeranthemum cylindraceum and X. annum: chemical composition, antimicrobial activity, and chemotaxonomic implications.

Detailed GC and GC-MS analyses of the essential oils and Et2 O extracts of two Xeranthemum species - X. cylindraceum and X. annum - resulted in the identification of 254 components, in total. Terpenoids constituted the major part of both X. cylindraceum and X. annum essential oils and extracts (51.8-65.7%, and 50.7%, resp.). Among the sesquiterpenoids, the extracts of both investigated taxa contained the guaianolide xerantholide, its 11,13-dihydro derivatives, and two additional sesquiterpene lactones: an eudesmanolide, 11,13-dihydroisoalantolactone, and a pseudoguaianolide, confertin. The last two lactones and both isomers of 11,13-dihydroxerantholide have not been previously detected in Xeranthemum species. The isolated extracts of X. cylindraceum and X. annum were tested in a broth microdilution assay against a panel of microorganisms. The tested extracts demonstrated significant antimicrobial inhibitory activity, ranging from 30 to 260 µg/ml, being most active against Bacillus cereus and Staphylococcus aureus, an important human pathogen, with MIC close in value to those of chloramphenicol. Chemotaxonomic significance of the sesquiterpene lactones' distribution in the taxa investigated in this study and those detected earlier in phylogenetically close species (up to the level of the tribe Cardueae) was also discussed.

Toxic essential oils. Part IV: The essential oil of Achillea falcata L. as a source of biologically/pharmacologically active trans-sabinyl esters.

Herein we report on the comprehensive chemical analysis of the essential oils obtained from above- and underground parts of a previously unreported chemotype of Achillea falcata L. (Asteraceae) and, for the first time, on the biological/toxicological profile of its dominant/newly discovered volatile metabolites. Detailed spectral analyses, in combination with chemical synthesis and theoretical study, of selected constituents, enabled the identification of trans-sabinol and its esters - the formate, tiglate (new compounds), acetate, butanoate, isobutanoate, 2-methylbutanoate and 3-methylbutanoate - in both aerial and underground parts of A. falcata. Evaluation of acute toxicity in Artemia salina model, in vitro and in silico (molecular docking) evaluation of acetylcholinesterase inhibitory activity and in vivo (mice) evaluation of antinociceptive activity (hot plate, tail immersion and acetylcholine-induced abdominal writhing tests) of trans-sabinol and its esters suggested that they may interact with different targets in crustacean/mammalian organisms. Alongside moderate acute toxicity (LD50 (48 h) = 0.03-0.26 mmol/L), the tested compounds exert influence on both the peripheral and central nervous systems (in the hot plate test, trans-sabinyl tiglate, at 50 mg/kg, produced a 140% baseline increase 15 min after the treatment) and to moderately inhibit acetylcholinesterase (at the concentration of 20 µg/mL, these compounds caused a reduction of acetylcholinesterase activity up to 40%).

Volatiles of Geranium purpureum Vill. and Geranium phaeum L.: chemotaxonomy of balkan Geranium and Erodium species (Geraniaceae).

The essential oils obtained by hydrodistillation of Geranium purpureum and G. phaeum were characterized by GC-FID and GC/MS analyses (the former for the first time in general). In total, 154 constituents were identified, accounting for 89.0-95.8% of the detected GC peak areas. The investigated essential oils consisted mainly of fatty acids and fatty-acid-derived compounds (45.4-81.3%), with hexadecanoic acid and (E)-phytol as the major components. The chemotaxonomic significance of the variations in the essential-oil composition/production of the presently and previously investigated Geranium and highly related Erodium taxa from Serbia and Macedonia was assessed by multivariate statistical analyses. The main conclusions drawn from the high chemical similarity of the two genera, visible from the obtained dendrograms and biplots, confirm the close phylogenetic relationship between the investigated Geranium and Erodium taxa, i.e., that there is no great intergeneric oil-composition variability. Changes in the composition and production of essential oils of the herein investigated taxa and 60 other randomly chosen species belonging to different plant genera were also statistically analyzed. The results put forward pro arguments for the oil-yield-oil-composition correlation hypothesis.

Toxic essential oils: anxiolytic, antinociceptive and antimicrobial properties of the yarrow Achillea umbellata Sibth. et Sm. (Asteraceae) volatiles.

Many plant species are used for medicinal purposes without the knowledge of their possible toxic effect. The ethnopharmacologically renowned genus Achillea L. (Asteraceae) is even more troublesome in this respect since different taxa are believed to have the same beneficial properties as A. millefolium. According to the median lethal i.p. dose (LD(50)=853 mg/kg, mice), the volatiles of Achillea umbellata Sibth. et Sm. are more toxic than the thujone-containing essential oils (LD(50)>960 mg/kg). A GC-MS analysis of A. umbellata oil revealed the presence of a series of fragranyl esters (six new natural products). The major constituents of this oil, the rare monoterpene alcohol fragranol and fragranyl acetate, and one more ester (benzoate), as well as the oil itself, showed antianxiety, analgesic and, in some instances, paralyzing properties at 50-150 mg/kg but these are very likely sign of intoxication and not of possible beneficial effects of the plant volatiles. Testing of antimicrobial activity demonstrated that the oil possesses moderate activity against pathogenic microorganisms, but the effect of the oil differs in pro- and eukaryotic cells. According to the results obtained, fragranol may be considered as the main active principle responsible for the observed activity/toxicity.

Geranium macrorrhizum L. (Geraniaceae) essential oil: a potent agent against Bacillus subtilis.

The volatile hydrodistilled compounds from aerial parts and rhizomes of the ethnopharmacologically highly valued plant species Geranium macrorrhizum L. were screened for their antimicrobial activity in disc-diffusion and microdilution assays. The assays pointed out to a very high and selective activity of the oils against Bacillus subtilis with minimum inhibitory concentrations (MIC) of 0.4-1.0 µg/ml. This prompted us to perform detailed compositional analyses of the oils. GC and GC/MS analyses allowed the identification of 283 constituents. The oils consisted mainly of sesquiterpenoids, the main ones being germacrone (49.7% in the oil from aerial parts) and δ-guaiene (49.2% in rhizome oil). Significant qualitative and quantitative compositional differences in the oils from the two plant parts were observed. Further antimicrobial testing enabled us to determine that germacrone, the major constituent of the oil from aerial parts, was not the sole agent responsible for the observed activity.