New advances in the volatile metabolites of Frullania tamarisci

First Phytochemical Profiling and In-Vitro Antiprotozoal Activity of Essential Oil and Extract of Plagiochila porelloides

Volatiles metabolites from the liverwort Plagiochila porelloides harvested in Corsica were investigated by chromatographic and spectroscopic methods. In addition to already reported constituents, three new compounds were isolated by preparative chromatography and their structures were elucidated by mass spectrometry (MS) and NMR experiments. Hence, an atypic aliphatic compound, named 1,2-dihydro-4,5-dehydronerolidol and two isomers, (E) and (Z), possessing an unusual humbertiane skeleton (called p-menth-1-en-3-[2-methylbut-1-enyl]-8-ol) are newly reported and fully characterized in this work. The in vitro antiprotozoal activity of essential oil and extract of P. porelloides against Trypanosoma brucei brucei and Leishmania mexicana mexicana and cytotoxicity were determined. Essential oil and Et₂O extract showed a moderate activity against T. brucei with IC₅₀ values: 2.03 and 5.18 μg/mL, respectively. It is noteworthy that only the essential oil showed a high selectivity (SI = 11.7). Diethyl oxide extract exhibited moderate anticancer (cancerous macrophage-like murine cells) activity and also cytotoxicity (human normal fibroblast) with IC₅₀ values: 1.25 and 2.96 μg/mL, respectively.

Guaianolide Derivatives from the Invasive Xanthium spinosum L.: Evaluation of Their Allelopathic Potential

Ziniolide, xantholide B (11α-dihydroziniolide), and 11β-dihydroziniolide, three sesquiterpene lactones with 12,8-guaianolide skeletons, were identified as volatile metabolites from the roots of Xanthium spinosum L., an invasive plant harvested in Corsica. Essential oil, as well as hydrosol and hexane extracts, showed the presence of guaianolide analogues. The study highlights an analytical strategy involving column chromatography, GC-FID, GC-MS, NMR (1D and 2D), and the hemi-synthesis approach, to identify compounds with incomplete or even missing spectral data from the literature. Among them, we reported the 1H- and 13C-NMR data of 11β-dihydroziniolide, which was observed as a natural product for the first time. As secondary metabolites were frequently involved in the dynamic of the dispersion of weed species, the allelopathic effects of X. spinosum root's volatile metabolites were assessed on seed germination and seedling growth (leek and radish). Essential oil, as well as hydrosol- and microwave-assisted extracts inhibited germination and seedling growth; root metabolite phytotoxicity was demonstrated. Nevertheless, the phytotoxicity of root metabolites was demonstrated with a more marked selectivity to the benefit of the monocotyledonous species compared to the dicotyledonous species. Ziniolide derivatives seem to be strongly involved in allelopathic interactions and could be the key to understanding the invasive mechanisms of weed.

Qualitative profiling of mono- and sesquiterpenols in aglycon libraries from Vitis vinifera L. Gewürztraminer using multidimensional gas chromatography–mass spectrometry

In grape berries (Vitis vinifera L.), sesquiterpenes are mainly accumulated as hydrocarbons in the epicuticular wax layer of grapes, whereas monoterpenes, which are predominantly present as alcohols, are glycosylated and are stored as glycosides in the vacuoles of grape berry cells. In this study, extensive analysis of grape berry hydrolysates by means of comprehensive two-dimensional gas chromatography–time-of-flight–mass spectrometry demonstrated that glycosylated sesquiterpene alcohols show very little structural diversity when compared to the sesquiterpene hydrocarbon fraction in the cuticle and are glycosylated to a rather low extent when compared to monoterpenols. Twenty-four enzymatically released terpenols were found in hydrolysates of the aromatic white wine variety Gewürztraminer (V. vinifera subsp. vinifera) after previous solid-phase extraction and headspace solid-phase microextraction. The detection of only three sesquiterpene alcohols, namely farnesol, nerolidol and drimenol, shows that most sesquiterpene hydrocarbons do not have a related hydroxylated structure in grapes. Nevertheless, the presence of the acyclic aglycone farnesol and nerolidol may be of importance for the wine aroma, since these structural isomers can be converted into numerous sesquiterpenes by nonenzymatic acid-catalyzed reactions during wine production. Grape-derived glycosidically bound sesquiterpene alcohols, therefore, represent, in addition to free sesquiterpene hydrocarbons, another pool of compounds that may influence the aroma profile of wines.

Caution: Chemical Instability of Natural Biomolecules During Routine Analysis

Natural products (NPs) constitute a significant source of active biomolecules widely used in medicine, pharmacology and cosmetics. However, NPs structural characterization has the drawback of their chemical instability during the extraction steps and their likely transformation during the analytical protocol. In particular, tamariscol and conocephalenol are two compounds largely used in the cosmetic industry for their odorant properties. Thus, in the present study, we focused on the evolution of these two metabolites (extracted from Frullania tamarisci and Conocephalum conicum, respectively), as followed by NMR. Interestingly, we found that, once dissolved in deuterated chloroform, these two tertiary alcohols are both subjected to transformation processes, leading to degradation compounds with altered structures. Accordingly, these detected degradation compounds have been fully characterized by NMR and the experimental findings were supported by computational chemistry data.

Volatile Metabolites in Liverworts of Ecuador

Volatile metabolites from Frullania brasiliensis Raddi, Herbertus juniperoideus (Sw.) Grolle, Leptoscyphus hexagonus (Nees) Grolle, and Syzygiella anomala (Lindenb. & Gottsche) Steph collected in the south of Ecuador were investigated. Volatile secondary metabolites were extracted by hydrodistillation and analyzed by gas chromatography/flame ionization detector (GC/FID) and Gas chromatography/Mass spectrometry (GC/MS). Sixty-seven volatile compounds were identified in the four species, which represent between 80.12–90.17% of the total chemical composition. The major components were τ-muurolol (32.14%) and Germacrene-D (11.98%) in the essential oil of F. brasiliensis, bicyclogermacrene (18.23%), and Caryophyllene oxide (15.29%) in the oil of H. juniperoideus, Cabreuva oxide D (33.77%) and Elemol (18.55%) in the oil of Leptoscyphus hexagonus, and Silphiperfola-5,7(14)-diene (25.22%) and Caryophyllene oxide (8.98%) in the oil of Syzygiella anomala. This is the first report on volatile compounds for the species Herbertus juniperoideus, Leptoscyphus hexagonus, and Syzygiella anomala.