Synthesis of (R)- and (S)-10,16-dihydroxyhexadecanoic acid: cutin stereochemistry and fungal activation

NMR-Guided Isolation of Anti-inflammatory Carabranolides from the Fruits of Carpesium abrotanoides L

Carabranolides present characteristic NMR resonances for the cyclopropane moiety, which distinctly differ from those of other compounds and were used for an NMR-guided isolation in this study. As a result, 11 undescribed carabranolides (1-11), along with five known ones (12-16), were isolated from the fruits of Carpesium abrotanoides L. Compounds 1-11 are new esters of carabrol at C-4 with different carboxylic acids. Their structures were elucidated by HRESIMS and NMR spectroscopic data analysis. The biological evaluation showed that compounds 2-4, 15, and 16 exhibited significant inhibitory activity against LPS-induced NO release with an IC50 value of 5.6-9.1 μM and dose-dependently decreased iNOS protein expression in RAW264.7 cells.

Roles of the MYB94/FUSED LEAVES1 (ZmFDL1) and GLOSSY2 (ZmGL2) genes in cuticle biosynthesis and potential impacts on Fusarium verticillioides growth on maize silks

Maize silks, the stigmatic portions of the female flowers, have an important role in reproductive development. Silks also provide entry points for pathogens into host tissues since fungal hyphae move along the surface of the silks to reach the site of infection, i.e., the developing kernel. The outer extracellular surface of the silk is covered by a protective hydrophobic cuticle, comprised of a complex array of long-chain hydrocarbons and small amounts of very long chain fatty acids and fatty alcohols. This work illustrates that two previously characterized cuticle-related genes separately exert roles on maize silk cuticle deposition and function. ZmMYB94/FUSED LEAVES 1 (ZmFDL1) MYB transcription factor is a key regulator of cuticle deposition in maize seedlings. The ZmGLOSSY2 (ZmGL2) gene, a putative member of the BAHD superfamily of acyltransferases with close sequence similarity to the Arabidopsis AtCER2 gene, is involved in the elongation of the fatty acid chains that serve as precursors of the waxes on young leaves. In silks, lack of ZmFDL1 action generates a decrease in the accumulation of a wide number of compounds, including alkanes and alkenes of 20 carbons or greater and affects the expression of cuticle-related genes. These results suggest that ZmFDL1 retains a regulatory role in silks, which might be exerted across the entire wax biosynthesis pathway. Separately, a comparison between gl2-ref and wild-type silks reveals differences in the abundance of specific cuticular wax constituents, particularly those of longer unsaturated carbon chain lengths. The inferred role of ZmGL2 is to control the chain lengths of unsaturated hydrocarbons. The treatment of maize silks with Fusarium verticillioides conidia suspension results in altered transcript levels of ZmFDL1 and ZmGL2 genes. In addition, an increase in fungal growth was observed on gl2-ref mutant silks 72 hours after Fusarium infection. These findings suggest that the silk cuticle plays an active role in the response to F. verticillioides infection.

Unveiling the Hidden Properties of Tomato Peels: Cutin Ester Derivatives as Bio-Based Plasticizers for Polylactic Acid

Polylactic acid (PLA) is one of the most important biopolymers employed on the market due to its good mechanical strength and barrier properties. On the other hand, this material presents a rather low flexibility, limiting its employment. The valorization of bio-based agro-food waste for the modification of bioplastics is a highly appealing approach for the replacement of petrol-based materials. The aim of this work is to employ cutin fatty acids derived from a biopolymer (i.e., cutin), present in waste tomato peels and its bio-based derivatives as new plasticizers to enhance PLA flexibility. In particular, pure 10,16-dihydroxy hexadecanoic acid was extracted and isolated from tomato peels and then functionalized to give the desired compounds. All the molecules developed in this study were characterized by NMR and ESI-MS. Blends at different concentrations (10, 20, 30, and 40% w/w) the flexibility (T_g measurements with differential scanning calorimetry-DSC) of the final material. Furthermore, the physical behavior of two blends obtained by mechanical mixing of PLA and 16-methoxy,16-oxohexadecane-1,7-diyl diacetate was investigated through thermal and tensile tests. The data collected by DSC show a lowering in the T_g of all the blends of PLA with functionalized fatty acids, in comparison with pure PLA. Lastly, the tensile tests highlighted how PLA blended with 16-methoxy,16-oxohexadecane-1,7-diyl diacetate (20% w/w) can efficiently enhance its flexibility.

Analysis of volatile emissions from grape berries infected with Aspergillus carbonarius using hyphenated and portable mass spectrometry

Mycotoxins represent a serious risk for human and animal health. Οchratoxin A (OTA) is a carcinogenic mycotoxin produced by A. carbonarius that constitutes a severe problem for viticulture. In this study, we investigate the development of novel detection and on-line monitoring approaches for the detection of OTA in the field (i.e. out of the chemical laboratory) using advanced molecular sensing. Both stand-alone and hyphenated mass spectrometry (MS) based systems (e.g. Time-of-Flight ToF-MS and gas chromatography GC combined with MS) and compact portable membrane inlet MS (MIMS) have been employed for the first time to detect and monitor volatile emissions of grape berries infected by the fungus Aspergillus carbonarius. In vacuo (electron impact-EI) and ambient ionisation (electrospray ionisation-ESI) techniques were also examined. On-line measurements of the volatile emissions of grape berries, infected by various strains of A. carbonarius with different toxicity levels, were performed resulting in different olfactory chemical profiles with a common core of characteristic mass fragments, which could be eventually used for on-site detection and monitoring allowing consequent improvement in food security.

Insoluble and Thermostable Polyhydroxyesters From a Renewable Natural Occurring Polyhydroxylated Fatty Acid

To explore the potential of long chain polyhydroxyalkanoates as non-toxic food packaging materials, the characterization of polyesters prepared from a natural occurring polyhydroxylated C16 carboxylic acid (9,10,16-trihydroxyhexadecanoic or aleuritic acid) has been addressed. Such monomer has been selected to elucidate the reactivity of primary and secondary hydroxyl groups and their contribution to the structure and properties of the polyester. Resulting polyaleuritate films have been produced using an open mold in one-step, solvent-free self-polycondensation in melt state and directly in air to evaluate the effect of oxygen in their final physical and chemical properties. These polymers are amorphous, insoluble, and thermostable, being therefore suitable for solvent, and heat resistant barrier materials. Structurally, most of primary hydroxyls are involved in ester bonds, but there is some branching arising from the partial participation of secondary O-H groups. The oxidative cleavage of the vicinal diol moiety and a subsequent secondary esterification had a noticeable effect on the amorphization and stiffening of the polyester by branching and densification of the ester bond network. A derivation of such structural modification was the surface compaction and the reduction of permeability to water molecules. The addition of Ti(OiPr)₄ as a catalyst had a moderate effect, likely because of a poor diffusion within the melt, but noticeably accelerated both the secondary esterification and the oxidative processes. Primary esterification was a high conversion bulk reaction while oxidation and secondary esterification was restricted to nearby regions of the air exposed side of cast films. The reason was a progressive hindering of oxygen diffusion as the reaction progresses and a self-regulation of the altered layer growth. Despite such a reduced extent, the oxidized layer noticeably increased the UV-vis light blockage capacity. In general, characterized physical properties suggest a high potential of these polyaleuritate polyesters as food preserving materials.

The intimate talk between plants and microorganisms at the leaf surface

The plant epidermis or cuticle is constantly exposed to external and internal environmental factors, including an enriched and diverse community of bacteria, yeast, fungi, viruses, and mites. It is not only where the plant has its first physical barrier, but also where organisms can be recognized and potentially where the plant defense responses can be triggered. The plant cuticle is a polymeric composite formed by an array of structurally and chemically heterogeneous compounds, including cutin and wax. A few studies have shown that cuticular components are essential and important drivers of the structure and size of the bacterial community. On the other hand, cuticular components are also important for both pathogens and plants, to initiate the pre-invasion and infection process and to activate the innate immune response, respectively. In this review, we explore current knowledge on the role of the cuticle during the intimate interactions between plants and microorganisms, in particular pathogenic and non-pathogenic bacteria and fungi. Finally, we propose new perspectives on the potential use of this information for agriculture.

The cuticle and plant defense to pathogens

The cuticle provides a physical barrier against water loss and protects against irradiation, xenobiotics, and pathogens. Components of the cuticle are perceived by invading fungi and activate developmental processes during pathogenesis. In addition, cuticle alterations of various types induce a syndrome of reactions that often results in resistance to necrotrophs. This article reviews the current knowledge on the role of the cuticle in relation to the perception of pathogens and activation of defenses.

Oligomerization of 10,16-dihydroxyhexadecanoic acid and methyl 10,16-dihydroxyhexadecanoate catalyzed by lipases

The main monomer of tomato cuticle, 10,16-dihydroxyhexadecanoic acid (10,16-DHPA) and its methyl ester derivative (methyl-10,16-dihydroxyhexadecanote; methyl-10,16-DHHD), were used to study their oligomerization reactions catalyzed by five lipases: Candida antarctica lipase B (CAL-B), Rhizomucor miehei lipase (RM), Thermomyces lanuginosus lipase (TL), Pseudomonas cepacia lipase (PCL) and porcine pancreatic lipase (PPL). For 10,16-DHPA, optimum yields were obtained at 60 °C using toluene and 2-methyl-2-butanol (2M2B) as solvent, while for methyl-10,16-DHHD the bests yields were obtained in toluene and acetonitrile. Both reactions leaded to linear polyesters according to the NMR and FT-IR analysis, and there was no data indicating the presence of branched polymers. Using optimized conditions, poly(10,16-DHPA) and poly(methyl-10,16-DHHD) with Mw = 814 and Mn = 1,206 Da, and Mw = 982 and Mn = 860 Da, respectively, were formed according to their MALDI-TOF MS and ESI-MS data. The self-assembly of the polyesters obtained were analyzed by AFM.

Derivatives of 10,16-dihydroxyhexadecanoic acid isolated from tomato (Solanum lycopersicum) as potential material for aliphatic polyesters

The main monomer of tomato cuticle, 10,16-dihydroxyhexadecanoic acid (or 10,16-dihydroxypalmitic acid; 10,16-DHPA), was isolated and used to efficiently synthesize two different monomers (16-hydroxy-10-oxo-hexadecanoic and 7-oxohexa-decanedioic acids) in addition to a dimer and linear and branched trimers. These compounds were fully characterized using NMR and MS techniques and could be used as starting materials for the synthesis of a wide range of chemicals and bio-polyesters, particularly the latter due to their physical properties, non-toxicity, and relative abundance among raw materials.

Plant Surface Properties in Chemical Ecology

The surface of the primary aerial parts of terrestrial plants is covered by a cuticle, which has crucial autecological functions, but also serves as an important interface in trophic interactions. The chemical and physical properties of this layer contribute to these functions. The cuticle is composed of the cuticular layer and the cuticle proper, which is covered by epicuticular waxes. Whereas the cutin fraction is a polyester-type biopolymer composed of hydroxyl and hydroxyepoxy fatty acids, the cuticular waxes are a complex mixture of long-chain aliphatic and cyclic compounds. These highly lipophilic compounds determine the hydrophobic quality of the plant surface and, together with the microstructure of the waxes, vary in a species-specific manner. The physicochemical characteristics contribute to certain optical features, limit transpiration, and influence adhesion of particles and organisms. In chemical ecology, where interactions between organisms and the underlying (allelo-) chemical principles are studied, it is important to determine what is present at this interface between the plant and the environment. Several useful equations can allow estimation of the dissolution of a given organic molecule in the cuticle and its transport properties. The implementation of these equations is exemplified by examining glucosinolates, which play an important role in interactions of plants with other organisms. An accurate characterization of physicochemical properties of the plant surface is needed to understand its ecological significance. Here, we summarize current knowledge about the physical and chemical properties of plant cuticles and their role in interactions with microorganisms, phytophagous insects, and their antagonists.

Novel chemoenzymatic strategy for the synthesis of enantiomerically pure secondary alcohols with sterically similar substituents

A novel chemoenzymatic strategy for the synthesis of enantiomerically pure secondary alcohols with sterically similar substituents is described. The key step is the kinetic lipase-catalyzed resolution of racemic mixtures of substituted propargylic alcohols. The efficiency of this new approach was tested in the preparation of the corresponding enantiomers of 1,11-hexadecandiol derivatives ((R)-5 and (S)-5). Two strategies were tested. In the first one, the racemic intermediate 1-octyn-3-ol (1) was resolved enzymatically and then elongated with 1-bromo-9,11-dioxadodecane. Alternatively, the racemic 1 can be elongated to the corresponding racemic 17,19-dioxa-7-eicosyn-6-ol (3) first and then resolved biocatalytically. Twelve commercially available lipases were screened for the kinetic resolution of these intermediates. Among them, Candida antarctica lipase (CAL-B) and Humicola lanuginosa lipase (HLL) were the best biocatalysts for the resolution of 1 (S enantiomer 90% ee, E = 35), and 3 (R enantiomer 90% ee, E = 34), respectively.