Benzyl Isothiocyanate, a Major Component from the Roots of Salvadora Persica Is Highly Active against Gram-Negative Bacteria

Plants produce a number of antimicrobial substances and the roots of the shrub Salvadora persica have been demonstrated to possess antimicrobial activity. Sticks from the roots of S. persica, Miswak sticks, have been used for centuries as a traditional method of cleaning teeth. Diverging reports on the chemical nature and antimicrobial repertoire of the chewing sticks from S. persica led us to explore its antibacterial properties against a panel of pathogenic or commensal bacteria and to identify the antibacterial component/s by methodical chemical characterization. S. persica root essential oil was prepared by steam distillation and solid-phase microextraction was used to sample volatiles released from fresh root. The active compound was identified by gas chromatography-mass spectrometry and antibacterial assays. The antibacterial compound was isolated using medium-pressure liquid chromatography. Transmission electron microscopy was used to visualize the effect on bacterial cells. The main antibacterial component of both S. persica root extracts and volatiles was benzyl isothiocyanate. Root extracts as well as commercial synthetic benzyl isothiocyanate exhibited rapid and strong bactericidal effect against oral pathogens involved in periodontal disease as well as against other Gram-negative bacteria, while Gram-positive bacteria mainly displayed growth inhibition or remained unaffected. The short exposure needed to obtain bactericidal effect implies that the chewing sticks and the essential oil may have a specific role in treatment of periodontal disease in reducing Gram-negative periodontal pathogens. Our results indicate the need for further investigation into the mechanism of the specific killing of Gram-negative bacteria by S. persica root stick extracts and its active component benzyl isothiocyanate

Uncoupled activation and cyclization in catmint reductive terpenoid biosynthesis

Terpene synthases typically form complex molecular scaffolds by concerted activation and cyclization of linear starting materials in a single enzyme active site. Here we show that iridoid synthase, an atypical reductive terpene synthase, catalyzes the activation of its substrate 8-oxogeranial into a reactive enol intermediate, but does not catalyze the subsequent cyclization into nepetalactol. This discovery led us to identify a class of nepetalactol-related short-chain dehydrogenase enzymes (NEPS) from catmint (Nepeta mussinii) that capture this reactive intermediate and catalyze the stereoselective cyclisation into distinct nepetalactol stereoisomers. Subsequent oxidation of nepetalactols by NEPS1 provides nepetalactones, metabolites that are well known for both insect-repellent activity and euphoric effect in cats. Structural characterization of the NEPS3 cyclase reveals that it binds to NAD+ yet does not utilize it chemically for a non-oxidoreductive formal [4 + 2] cyclization. These discoveries will complement metabolic reconstructions of iridoid and monoterpene indole alkaloid biosynthesis

Synthesis and characterization of the four geometrical isomers of 3,5-dodecadienyl acetate

Practical convergent syntheses of the four geometrical isomers of 3,5-dodecadienyl acetate are presented. These substances have been characterized by NMR and mass spectroscopy. (3E,5Z)-3,5-Dodecadienyl acetate is the main female sex pheromone component of the leaf roller Bonagota cranaodes, which is an important insect pest in apples in South America. The isomeric 3,5-dodecadienyl acetates, as pure isomers and in defined mixtures, have been used as trap lures for Eying insects in field screening experiments in Lithuania. Although no insects were found in the control traps, the numbers of males caught in the baited traps were not high enough to be statistically significant

Detection of sex pheromone components in Manduca sexta (L.)

The ability of olfactory receptor neurons to detect female-produced sex pheromone components and a limited sample of potential host plant odours was studied by single-sensillum recordings from olfactory sensilla present on male and female antennae in Manduca sexta, The majority of pheromone-sensitive receptor neurons examined in males was specialized for detection of the two major pheromone components, E10,Z12-hexadecadienal and E10,E12,Z14-hexadecatrienal or E10,E12,E14-hexadecatrienal. New olfactory receptor neurons tuned to the minor components E10,E12-hexadecadienal and Z11-hexadecenal were found. in females, olfactory receptor neurons specific to Z11-hexadecanal were discovered. Pheromone components and host volatiles were detected by separate sets of receptor neurons

Biosourced All-Acrylic ABA Block Copolymers with Lactic Acid-Based Soft Phase

16 pags., 9 figs.Lactic acid is one of the key biobased chemical building blocks, given its readily availability from sugars through fermentation and facile conversion into a range of important chemical intermediates and polymers. Herein, well-defined rubbery polymers derived from butyl lactate solvent were successfully prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization of the corresponding monomeric acrylic derivative. Good control over molecular weight and molecular weight distribution was achieved in bulk using either monofunctional or bifunctional trithiocarbonate-type chain transfer agents. Subsequently, poly(butyl lactate acrylate), with a relative low Tg (-20 °C), good thermal stability (5% wt. loss at 340 °C) and low toxicity was evaluated as a sustainable middle block in all-acrylic ABA copolymers using isosorbide and vanillin-derived glassy polyacrylates as representative end blocks. Thermal, morphological and mechanical properties of copolymers containing hard segment contents of <20 wt% were evaluated to demonstrate the suitability of rubbery poly(alkyl lactate) building blocks for developing functional sustainable materials. Noteworthy, 180° peel adhesion measurements showed that the synthesized biosourced all-acrylic ABA copolymers possess competitive performance when compared with commercial pressure-sensitive tapes.This research was funded by Spanish Ministerio de Ciencia, Innovación y Universidades through project MAT2017-82669-R (to G.L. and J.C.R.), Serra Hunter Programme of the Government of Catalonia (to G.L.), University Rovira i Virgili (DL003536 grant to N.B.), Miguel Servet Program from Instituto de Salud Carlos III (CPII13/00017 to O.A.), Fondo de Investigaciones Sanitarias from Instituto de Salud Carlos III, and European Union (ERDF/ESF, ‘Investing in your future’) (PI18/00349 to O.A.), Diputación General de Aragón (Predoctoral Research Contract 2019 to A.J.-A., ‘Digestive Pathology Group’ B25_20R to O.A.), and Centro de Investigación Biomédica en Red en Enfermedades Hepáticas y Digestivas (CIBERehd). I.L. and L.V. gratefully acknowledge support from the European Regional Development Fund (No. MOBTT21), the Estonia-Russia Cross Border Cooperation Programme (ER30) and the Baltic Research Programme in Estonia (EEA grant no. EMP426