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.

The essential oil of the condiment species Clinopodium thymifolium (Scop.) Kuntze: new natural products and seasonal variation.

BACKGROUND: Clinopodium thymifolium is an aromatic plant species that is widespread in the Mediterranean region. It has been considered as a condiment and is used in cooking. As a promising spice plant, some efforts are being made to introduce this plant as a new crop species and it has been successfully cultivated in northern Italy. RESULTS: Essential oils isolated from the aerial parts of a flavoring species C. thymifolium were analyzed by gas chromatography and gas chromatography/mass spectrometry. The results of a detailed analysis of the chemical composition of the oils showed the domination of pulegone, piperitone, piperitenone and isomenthone, as well as a significant alteration of the pulegone/isomenthone ratio with the developmental stage of the plant. Additionally, a comprehensive chemical analysis of the oils in combination with detailed spectral analyses and chemical synthesis of selected compounds has led to the identification of two new natural products: isomenthyl formate and neomenthyl 2-methylbutanoate. CONCLUSION: The observed chemical variability at the intrapopulation level appeared to be a phenological variation. In an evolutionary sense, the alteration of the pulegone/isomenthone ratio suggests their possible role in the ecological adaptation of the species to pollinators. Significant quantitative changes in the chemical composition of the oil at different phenological stages may be relevant in the case of plant material intended for edible purposes. © 2021 Society of Chemical Industry.

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.

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%).

Chemotaxonomy of Serbian Teucrium species inferred from essential oil chemical composition: the case of Teucrium scordium L. ssp. scordioides.

The volatile constituents of Teucrium scordium L. ssp. scordioides, T. polium, and T. montanum, obtained by hydrodistillation, were investigated by GC-FID and GC/MS analyses. A total of 296 constituents were identified, representing 89.8-98.4% of the oil compositions. The oils of T. polium and T. montanum consisted mainly of sesquiterpenes (64.3 and 72.7%, resp.), with germacrene D (4; 31.0%) and δ-cadinene (10; 8.1%) as the main constituents, respectively. In contrast, the monoterpene menthofuran (1; 11.9%) predominated in the oil of T. scordium ssp. scordioides, and this clearly distinguished this species from the other Teucrium taxa investigated up to date. The chemistry of the volatiles of eight Teucrium taxa from Serbia and Montenegro were compared using multivariate statistical analysis, and this provided chemotaxonomically important conclusions.

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.