Identification of Granatane Alkaloids from Duboisia myoporoides (Solanaceae) using Molecular Networking and Semisynthesis.

The Solanaceae plant family contains at least 98 genera and over 2700 species. The Duboisia genus stands out for its ability to produce pyridine and tropane alkaloids, which are relatively poorly characterized at the phytochemical level. In this study, we analyzed dried leaves of Duboisia spp. using supercritical CO2 extraction and ultra-high-pressure liquid chromatography coupled to high-resolution tandem mass spectrometry, followed by feature-based molecular networking. Thirty-one known tropane alkaloids were putatively annotated, and the identity of six (atropine, scopolamine, anisodamine, aposcopolamine, apoatropine, and noratropine) were identified using reference standards. Two new granatane alkaloids connected in the molecular network were highlighted from Duboisia myoporoides, and their α-granatane tropate and α-granatane isovalerate structures were unambiguously established by semisynthesis.

Isolation and Structure Determination of Drought-Induced Multihexose Benzoxazinoids from Maize (Zea mays).

Benzoxazinoids (BXDs) are plant specialized metabolites exerting a pivotal role in plant nutrition, allelopathy, and defenses. Multihexose benzoxazinoids were previously observed in cereal-based food products such as whole-grain bread. However, their production in plants and exact structure have not been fully elucidated. In this study, we showed that drought induced the production of di-, tri-, and even tetrahexose BXDs in maize roots and leaves. We performed an extensive nuclear magnetic resonance study and elucidated the nature and linkage of the sugar units, which were identified as gentiobiose units ß-linked (1″ → 6') for the dihexoses and (1″ → 6')/(1‴ → 6″) for the trihexoses. Drought induced the production of DIMBOA-2Glc, DIMBOA-3Glc, HMBOA-2Glc, HMBOA-3Glc, and HDMBOA-2Glc. The induction was common among several maize lines and the strongest in seven-day-old seedlings. This work provides ground to further characterize the BXD synthetic pathway, its relevance in maize-environment interactions, and its impact on human health.

Non-canonical Biosynthesis of the Brexane-Type Bishomosesquiterpene Chlororaphen through Two Consecutive Methylation Steps in Pseudomonas chlororaphis O6 and Variovorax boronicumulans PHE5-4.

A non-canonical biosynthetic pathway furnishing the first natural brexane-type bishomosesquiterpene (chlororaphen, C17 H28 ) was elucidated in the γ-proteobacterium Pseudomonas chlororaphis O6. A combination of genome mining, pathway cloning, in vitro enzyme assays, and NMR spectroscopy revealed a three-step pathway initiated by C10 methylation of farnesyl pyrophosphate (FPP, C15 ) along with cyclization and ring contraction to furnish monocyclic γ-presodorifen pyrophosphate (γ-PSPP, C16 ). Subsequent C-methylation of γ-PSPP by a second C-methyltransferase furnishes the monocyclic α-prechlororaphen pyrophosphate (α-PCPP, C17 ), serving as the substrate for the terpene synthase. The same biosynthetic pathway was characterized in the ß-proteobacterium Variovorax boronicumulans PHE5-4, demonstrating that non-canonical homosesquiterpene biosynthesis is more widespread in the bacterial domain than previously anticipated.

Evaluation of Ruthenium-Based Assemblies as Carriers of Photosensitizers to Treat Rheumatoid Arthritis by Photodynamic Therapy.

For the first time, ruthenium-based assemblies have been used as carriers for photosensitizers in the treatment of rheumatoid arthritis by photodynamic therapy (PDT). These metallacages are totally soluble in physiological media and can transport photosensitizers (PS) in their cavity. After an incubation period, the PS is released in the cytoplasm and irradiation can take place. This strategy allows photosensitizers with low or null solubility in biological media to be evaluated as PDT agents in rheumatoid arthritis. The systems in which 21H,23H-porphine and 29H,31H-phthalocyanine are encapsulated show excellent photocytotoxicity and no toxicity in the dark. On the other hand, systems in which metalated derivatives such as Mg(II)-porphine and Zn(II)-phthalocyanine are used show good photocytotoxicity, but to a lesser extent than the previous two. Furthermore, the presence of Zn(II)-phthalocyanine significantly increases the toxicity of the system. Overall, fifteen different host-guest systems have been evaluated, and based on the results obtained, they show high potential for treating rheumatoid arthritis by PDT.

Epimerization of an Ascaroside-Type Glycolipid Downstream of the Canonical ß-Oxidation Cycle in the Nematode Caenorhabditis nigoni.

A species-specific ascaroside-type glycolipid was identified in the nematode Caenorhabditis nigoni using HPLC-ESI-(-)-MS/MS precursor ion scanning, HR-MS/MS, and NMR techniques. Its structure containing an l-3,6-dideoxy-lyxo-hexose unit was established by total synthesis. The identification of this novel 4-epi-ascaroside (caenorhabdoside) in C. nigoni along with the previous identification of 2-epi-ascarosides (paratosides) in Pristionchus pacificus indicate that nematodes can generate highly specific signaling molecules by epimerization of the ascarylose building block downstream of the canonical ß-oxidation cycle.

Essential oil of the malagasy grass Elionurus tristis Hack. contains several undescribed sesquiterpenoids.

Essential oils (EOs) obtained from aerial parts and roots of Elionurus tristis were investigated by GC, GC-MS, pc-GC and NMR. Both aerial parts and roots EOs contained common molecules such as α-pinene, camphene, trans-α-bergamotene and calarene. Moreover, we identified several unusual sesquiterpenes and four undescribed compounds, 7-epi-khusian-2-ol, 4,8-di-epi-acorone, 2-epi-ziza-5-en-2-ol and antsorenone. The last one exhibits an undescribed natural sesquiterpene skeleton. All undescribed compounds were isolated and fully characterized by MS, 1D and 2D-NMR. Furthermore, the formation pathway of the Antsorane skeleton is discussed.

Anti-Quorum Sensing Activity of 12 Essential Oils on chromobacterium violaceum and Specific Action of cis-cis-p-Menthenolide from Corsican Mentha suaveolens ssp. Insularis.

Quorum sensing (QS) is a bacterial communication mechanism used to express various survival or virulence traits leading to enhanced resistance. Chromobacterium violaceum is a commonly used strain that highlights anti-QS action of bioactive substances. Here, we wanted to see if 12 selected essential oils (EO) could exert anti-QS activity. We measured the sublethal minimal QS inhibitory concentration (MQSIC) by assessing violacein production of C. violaceum along with bacterial growth. To confirm the QS disruption, we also proceed to surface bacterial observations using scanning electron microscopy (SEM). We showed that cis-cis-p-menthenolide extracted and isolated from a plant endemic to occidental Mediterranean Sea islands, Mentha suaveolens ssp. insularis, acts as an inhibitor of violacein production and biofilm formation. Measured MQSIC was much lower than the minimal inhibitory concentration (MIC): 0.10 mg·mL-1 vs. 3.00 mg·mL-1. Moreover, disturbance of QS-related traits was confirmed by the degradation of C. violaceum biofilm matrix. There is a clear structure⁻activity relationship between cis-cis-p-menthenolide and anti-QS activity. Indeed, its isomer molecule (mintlactone) exerts a poor anti-QS action. These results indicate that inhibition of violacein production and biofilm formation by cis-cis-p-menthenolide might be related to a disruption in the QS mechanism.

New Metabolites Isolated from a Laurencia obtusa Population Collected in Corsica.

The chemical investigation of an ethyl acetate extract (EtOAc) obtained from Laurencia obtusa, collected in Corsica, allowed for the identification of three new compounds (1, 2, and 4) and six known compounds. Compounds 1 to 4 were isolated and fully characterized by a detailed spectroscopic analysis. Compounds 1 and 2 are two C15-acetogenins sharing the same ring system: a tetrahydropyran linked by a methylene to a tetrahydrofuran ring. Compound 1 exhibits a bromoallene unit whereas compound 2 possesses an uncommon α-bromo-α,ß-unsaturated aldehyde terminal unit. Compound 4 is the first diterpene exhibiting a 19(4 → 3)abeo-labdane skeleton isolated from a Laurencia species. Isolation of concinndiol (compound 3) together with compound 4 suggests a common biosynthetic origin. Additionally, five known compounds, namely sagonenyne, laurene, α-bromocuparene, microcladallene A, and ß-snyderol were identified in chromatographic fractions by NMR analysis using a computerized method that was developed in our laboratory.

Halogenated C15 Acetogenin Analogues of Obtusallene III from a Laurenciella sp. Collected in Corsica.

NMR chemical profiling of a Laurenciella sp. using a computerized method developed in our laboratory resulted in the identification of five new compounds (1-5) and 17 known compounds, among which 3-(E)-laurenyne represented by far the most abundant metabolite. Compounds 1 to 5 were isolated and fully characterized by detailed spectroscopic analysis. The absolute configuration and structural features of compound 1 were determined by single-crystal X-ray diffraction analysis. Compounds 1 to 4 are 12-membered cyclic ether acetogenins that are present in solution as interconverting conformers exhibiting an (aR) configuration of the bromoallene unit together with an S configuration at C-4. Among these, compound 3 is the first obtusallene derivative with bromine substituents at both the C-7 and C-12 positions. Compound 5 is an acetogenin bearing a [5.5.1]bicyclotridecane ring system. A plausible biosynthetic route to 1-4 is proposed.

Discrimination and Characterization of Two Mediterranean Species from the Laurencia Complex (Rhodomelacea) Using an NMR-Based Metabolomic Approach.

Generic and specific determination among the Laurencia complex is a challenging task. DNA barcoding combined with phenotypic investigations are mandatory for species differentiation. In this study, two morphologically different members of the Laurencia complex were investigated using untargeted 1 H-NMR-based metabolomics. Twenty-one population samples were collected in order to evaluate both temporal and geographical homogeneity. Data obtained from 1 H-NMR analysis followed by statistical analysis allowed a clear separation of all the samples into two groups. DNA mitochondrial tests confirmed this pattern and identified the two species as Laurenciella sp. and Laurencia obtusa. In addition, metabolites responsible of this discrimination were investigated directly in crude extracts by 13 C-NMR using an in-house computer-assisted method. The combination of both untargeted (1 H) and targeted (13 C) NMR-based metabolomic approaches proves to be a powerful and complementary approach to discriminate species from the Laurencia complex.

Chemical Composition of Laurencia obtusa Extract and Isolation of a New C15-Acetogenin.

A new C15-acetogenin, sagonenyne (20), exhibiting an unusual single tetrahydropyran ring was isolated from an ethyl acetate extract of Laurencia obtusa collected on the Corsican coastline. Its structure was established by detailed NMR spectroscopic analysis, mass spectrometry, and comparison with literature data. Twenty-three known compounds were identified in the same extract by means of column chromatography steps, using a 13C-NMR computer aided method developed in our laboratory. In addition to sesquiterpenes, which represent the main chemical class of this extract, diterpenes, sterols, and C15-acetogenins were identified. The crude extract was submitted to a cytotoxicity assay and was particularly active against THP-1 cells, a human leukemia monocytic cell line.

Integrated Analysis by GC(RI), GC-MS and 1C NMR of Fortunella japonica Leaf Volatiles Obtained by Hydrodistillation, Microwave- assisted Hydrodistillation and Hydrolate Extraction.

The chemical composition of the essential oil (EO), microwave extract (ME) and hydrolate extract (HE) from the same batch of leaves of Fortunella japonica, was investigated: by combination of chromatographic (GC, CC) and spectroscopic techniques (GC-MS, 13C NMR). F. japonica essential oil and extracts are complex mixtures of 28-60 compounds being mainly oxygenated sesquiterpenes. The EO composition was dominated by germacrene D (14.9%), ß-elemol (9.1%), cis-guai-6-en-10ß-ol (6.3%), ß-eudesmol (5.5%), and δ-elemene (5.2%). Limonene was the unique monoterpene identified at appreciable amount (7.1%). The extract obtained by microwave assisted hydrodistillation contained as main components: ß-elemol (12.4%), germacrene D (9.9%), cis-guai-6-en- 10ß-ol (9.0%), ß-eudesmol (8.2%), germacra-l(l0),5-dien-4α-ol (7.1%) and α-eudesmol (6.4%). Finally, the highest content of oxygenated sesquiterpenes (near 92%) was found in the hydrolate extract displaying cryptomeridiol (23.3%, but totally absent in the EO and ME), ß-eudesmol (20.6%) and α-eudesmol (10.7%). Combined analysis by chromatographic and spectroscopic techniques appeared useful for identification of various sesquiterpenols bearing a tertiary alcohol function.

Chemical Composition of the Fruit Oils of Five Fortunella Species Grown in the Same Pedoclimatic Conditions in Corsica (France).

Fruit oil from five species of kumquat (Fortunella japonica, F. margarita, F. crassifolia, F. obovata, and F. hindsii) grown in the same pedoclimatic conditions have been analyzed by a combination of chromatographic and spectroscopic techniques. The compositions of the five fruit oils were strongly dominated by limonene (84.2-96.3%). Other components present with appreciable contents were myrcene (1.3-12.9%) and germacrene D (0.3-2.4%).

Composition and Chemical Variability of Ivoirian Xylopia staudtii Leaf Oil.

The chemical composition of a leaf oil sample from Ivoirian Xylopia staudtii Engler & Diels (Annonaceae) has been investigated by a combination of chromatographic [GC(RI)] and spectroscopic (GC-MS, 13C NMR) techniques. Thirty-five components that accounted for 91.8% of the whole composition have been identified. The oil composition was dominated by the furanoguaiadienes furanoguaia-1,4-diene (39.0%) and furanoguaia-1,3-diene(7.5%), and by germacrene D (17.5%). The composition of twelve other leaf oil samples demonstrated qualitative homogeneity, but quantitative variability. Indeed, the contents of the major components varied substantially: furanoguaia-1,4-diene (24.7-51.7%) and germacrene D (5.9-24.8%). The composition of X. staudtii leaf oil is close to that of X. rubescens leaf oil but varied drastically from those of the essential oils isolated from other Xylopia species. 13C NMR spectroscopy appeared as a powerful and complementary tool for analysis of sesquiterpene-rich essential oils.

Chemical composition of the essential oil from Corsican Mentha aquatica--combined analysis by GC(RI), GC-MS and 13C NMR spectroscopy.

The essential oil (EO) of M. aquatica L. growing wild in Corsica was isolated by dry vapor distillation and submitted to combined analysis by column chromatography over silica gel, GC(RI), GC-MS and 13C NMR spectroscopy. The composition was dominated byoxygenated monoterpenes and characterized by the occurrence of menthofuran (50.7%) as the major component. In parallel, seven laboratory-distilled oil samples isolated from individual plants collected in Corsica were analyzed by GC(RI) and 13C NMR spectroscopy. Onlyquantitative differences were observed between the samples. Beside the usual terpenes, various p-menthane lactones (mintlactone, isomintlactone, hydroxymintlactone, menthofurolactone and epimenthofurolactone) have been identified in all the oil samples.

Composition and chemical variability of Mentha suaveolens ssp. suaveolens and M. suaveolens ssp. insularis from Corsica.

A detailed analysis of two essential oils from individual plants of Mentha suaveolens ssp. suaveolens growing wild in Corsica was carried out by combination of GC(RI), GC/MS, and (13)C-NMR analyses. One oil sample is characterized by the pre-eminence of piperitenone oxide, and the second is dominated by piperitenone. In contrast, it was reported that the essential oil of M. suaveolens ssp. insularis, an endemic species to Corsica and Sardinia, contained pulegone and cis-cis-p-menthenolide as main components. A principal-component analysis (PCA) carried out on the composition of the essential oil of 59 individual plants of M. suaveolens sp. allowed the classification into three well-defined groups. All the oil samples from Mentha suaveolens ssp. insularis belonged to the same group, while the oils from M. suaveolens ssp. suaveolens were distributed in the two other groups. The composition of the essential oil isolated from aerial parts of M. suaveolens ssp. has been shown to be an additional tool to differentiate the botanically close subspecies suaveolens and insularis.