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.

Polyalthia longifolia produces sesquiterpene‐rich essential oils (EOs) whose compositions varied substantially from sample to sample depending on the origin of the plant (Nigeria and Vietnam). Nothing is known about the phytochemistry of Ivoirian P. longifolia. The aim of the present study was to characterize Ivoirian P. longifolia through the chemical composition of the leaf oil and to develop a strategy that allows the identification of minor oxygenated sesquiterpenes whose MS data are not compiled in commercial or laboratory‐constructed MS libraries. The EO was submitted to gas chromatography (GC) retention index (RI), GC‐mass spectrometry (MS) and ¹³C nuclear magnetic resonance (NMR) analysis. Then hydrocarbons and oxygenated components were separated and the oxygenated fraction was chromatographed on silica gel. The fractions were analysed by GC(RI) and ¹³C NMR. Seventy compounds accounting for 91.8% of the EO were identified. Sesquiterpene hydrocarbons, (E)‐β‐caryophyllene (27.8%), α‐zingiberene (20.0%) and allo‐aromadendrene (15.0%), were the major components. Various oxygenated sesquiterpenes whose MS data were not compiled in commercial and laboratory‐made MS libraries were identified by comparison of their chemical shift values in the spectrum of the fraction of CC with those reported in the literature and compiled in a laboratory‐constructed ¹³C NMR data library. The composition of the investigated Ivoirian P. longifolia oil sample presented similarities and differences with Nigerian and Vietnamese oils. Combined analysis of Ivoirian P. longifolia EO by chromatographic and spectroscopic techniques including ¹³C NMR without isolation of the components, appeared particularly efficient to identify minor components of EOs, whose MS spectra are insufficiently differentiated or MS data are not compiled in commercial and lab‐constructed MS libraries. Copyright © 2014 John Wiley & Sons, Ltd.

A detailed analysis of Mentha suaveolens ssp. insularis (Req.) Greuter essential oil (EO) and hydrolate extract (HE) was carried out by combination of GC–RI, GC–MS and ¹³C‐NMR spectroscopy. After fractionation by column chromatography, 51 components of the EO and 27 components of the HE, accounting for 96.1% and 98.3%, respectively, were identified. The main components were pulegone (44.4% and 14.8%) and cis‐cis‐p‐menthenolide (27.3% and 67.3%). This α‐methylen‐γ‐butyrolactone, reported for the first time as a natural product, was isolated and its structure elucidated by 1D and 2D NMR spectroscopy. Both EO and HE exhibited a fair antibacterial activity against Staphylococcus aureus and Bacillus cereus. Copyright © 2008 John Wiley & Sons, Ltd.

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.

A non‐canonical biosynthetic pathway furnishing the first natural brexane‐type bishomosesquiterpene (chlororaphen, C₁₇H₂₈) 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 β‐proteobacterium Variovorax boronicumulans PHE5‐4, demonstrating that non‐canonical homosesquiterpene biosynthesis is more widespread in the bacterial domain than previously anticipated.