Effect of Biotic and Abiotic Stresses on Plant Metabolic Pathways

Plants are prone to encounter some environmental stresses that include both biotic and abiotic. Plants in response to these stress conditions alter their metabolism at the genetic level with consequential effects at the metabolite production. Phenolic compounds, which are secondary metabolites are one such chemical entity which plays a significant role in various physiological processes of the plant. They are mainly formed by three different types of metabolic pathways that produce phenyl propanoid derivatives, flavonoids, terpenoids based on the needs of the plant and the rate of their production is solely dictated by the type of stress condition. A number of phenolic compounds like phytoalexins, phytoanticipins and nematicides exhibit negative response to biotic stress against several soil borne pathogens and nematodes. But some of the phenolic compounds like acetosyringone, umbelliferone, vanillyl alcohol, p-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid, apigenin and luteolin are found to exhibit beneficial effects to plants by encouraging rhizosphere formation particularly in Leguminosae family. Some of the ROS produced in various stress conditions are effectively dealt by various phenolics with antioxidant activity like hydroxyl benzoic acids and hydroxyl cinnamic acids. As the in vivo production of phenolics in plants is influenced by external factors it can certainly provide information for the adoption of agronomic practices to yield the full befits of commercial exploitation. As the in vivo production of phenolics in plants is influenced by external factors it can certainly provide information for the adoption of agronomic practices to yield the full befits of commercial exploitation.

Breeding Capsicum chinense Lines with High Levels of Capsaicinoids and Capsinoids in the Fruit

Capsaicinoids, which cause a hot sensation when eaten, are uniquely present in pepper (Capsicum sp.) and are biosynthesized by combining vanillyl amine with branched fatty acids. A mutation in the gene encoding putative aminotransferase (pAMT)—the enzyme that normally biosynthesizes the capsaicinoid precursor vanillyl amine—leads instead to the biosynthesis of vanillyl alcohol, which combines with branched fatty acids to form capsinoids. Here, we report a method for increasing the capsaicinoid and capsinoid contents using quantitative trait locus (QTL) alleles involved in capsaicinoid biosynthesis in the pericarps of extremely spicy peppers. QTLs for capsinoid contents were detected on chromosome 6 and 10 using an F2 population from ‘SNU11–001’ and ‘Bhut Jolokia (BJ)’ (‘SJ’). ‘SNU11–001’ contains high capsinoid contents and ‘BJ’ contains high capsaicinoid contents in both the placenta and pericarp. These QTLs overlapped QTL regions associated with pungency in the pericarp. ‘BJ’ was crossed also with ‘Habanero’ (‘HB’), which contains capsaicinoids mainly in the placenta, and the resulting (‘HJ’) F2 and F3 offspring with ‘BJ’ genotypes were selected based on QTL markers and the pericarp pungency phenotype. Similarly, F2 and F3 offspring with high capsinoid contents in the pericarp were selected in ‘SJ’ with reference to ‘BJ’ genotypes at the QTLs. Through continuous self-pollination, ‘SJ’ and ‘BJ’ lines with high capsinoid and capsaicinoid contents, respectively, in both the placenta and pericarp were developed. This study is the first to show that lines containing high levels of capsinoids and capsaicinoids can be bred using pericarp capsaicinoid biosynthesis genes.

Curing Behavior and Thermomechanical Performance of Bioepoxy Resin Synthesized from Vanillyl Alcohol: Effects of the Curing Agent

In order to reduce the dependency of resin synthesis on petroleum resources, vanillyl alcohol which is a renewable material that can be produced from lignin has been used to synthesize bioepoxy resin. Although it has been widely reported that the curing reaction and properties of the cured epoxies can be greatly affected by the molecular structure of the curing agents, the exact influence remains unknown for bioepoxies. In this study, four aliphatic amines with different molecular structures and amine functionalities, namely triethylenetetramine (TETA), Tris(2-aminoethyl)amine (TREN), diethylenetriamine (DETA), and ethylenediamine (EDA), were used to cure the synthesized vanillyl alcohol–based bioepoxy resin (VE). The curing reaction of VE and the physicochemical properties, especially the thermomechanical performance of the cured bioepoxies with different amine functionalities, were systematically investigated and compared using different characterization methods, such as DSC, ATR–FTIR, TGA, DMA, and tensile testing, etc. Despite a higher curing temperature needed in the VE–TETA resin system, the cured VE–TETA epoxy showed a better chemical resistance, particularly acidic resistance, as well as a lower swelling ratio than the others. The higher thermal decomposition temperature, storage modulus, and relaxation temperature of VE–TETA epoxy indicated its superior thermal stability and thermomechanical properties. Moreover, the tensile strength of VE cured by TETA was 1.4~2.6 times higher than those of other curing systems. In conclusion, TETA was shown to be the optimum epoxy curing agent for vanillyl alcohol–based bioepoxy resin.

New Constituents from the Leaves of Date Palm (Phoenix dactylifera L.) of Saudi Origin

The phytochemical analysis of the butanolic extract from the leaves of date palm of Saudi origin resulted in the isolation of three major constituents, oleanolic acid (1), vanillyl alcohol (2), and β-sitosterol-3-O-β-d-glucoside (3), which had not been isolated from this plant or previously reported. Together, compounds 1 and 2 account for 1.0% of the butanol extract, which represents 0.4% of the mass of the dried leaves. The isolation of other known compounds for this plant such as fatty acids, lutein, and sucrose was also achieved in this study. The characterization and identification of the isolated compounds were conducted on the basis of Fourier-transform infrared spectroscopy (FTIR), 1H and 13C nuclear magnetic resonance (NMR), liquid chromatography–mass spectrometry (LC–MS), and gas chromatography–mass spectrometry (GC–MS) analyses. The findings of the current study will definitely increase the knowledge about the contribution of the constituents of this plant to its well-known nutrition, corrosion inhibition, and antimicrobial properties.

Revisiting the condensation reaction of lignin in alkaline pulping with quantitativity part I: the simplest condensation between vanillyl alcohol and creosol under soda cooking conditions

The condensation reaction of lignin is believed to interfere with delignification in alkaline pulping processes, without any clear evidence, which has motivated us to quantitatively revisit it. This paper is the first of a series, and hence we employed the simplest model system using 4-hydroxymethyl-2-methoxyphenol (vanillyl alcohol, Va) and 2-methoxy-4-methylphenol (creosol, Cr) under soda cooking conditions. The α-5-type condensation product between these compounds [VaCr, 2-(4-hydroxy-3-methoxybenzyl)-6-methoxy-4-methylphenol] was identified and quantified as exclusive. VaCr was yielded with a mole amount of 24%, 46%, 62%, or 72% based on that of disappearing Va at a reaction time of 120 min when the ratio of the initial concentration of Cr to that of Va was 1.0, 2.5, 5.0, or 7.5, respectively. These yields and an HPLC analysis of the reaction solution obtained by a treatment of Va as the sole compound under the same soda cooking conditions suggested the formation of self-condensation products of Va even in the treatments containing Cr. The obtained results comprehensively suggested that the self-condensation of Va progresses more readily than the condensation between Va and Cr. The factors behind this will be the topic of our next paper.

Nano-Magnetic NiFe2O4 and Its Photocatalytic Oxidation of Vanillyl Alcohol—Synthesis, Characterization, and Application in the Valorization of Lignin

Here, we report on a phyto-mediated bimetallic (NiFe2O4) preparation using a Boswellia carterii extract, which was characterized by XRD, FT-IR, TGA, electron microscopy, magnetic spectroscopy, and Mössbauer spectroscopy measurements. The prepared nano-catalysts were tested for oxidation of lignin monomer molecules—vanillyl alcohol and cinnamyl alcohol. In comparison with previously reported methods, the nano NiFe2O4 catalysts showed high photocatalytic activity and selectivity, under visible light irradiation with a nitroxy radical initiator (2,2,6,6-tetramethylpiperidinyloxy or 2,2,6,6-tetramethylpiperidine 1-oxyl; TEMPO) at room temperature and aerobic conditions. The multifold advantages of the catalyst both in terms of reduced catalyst loading and ambient temperature conditions were manifested by higher conversion of the starting material.

Enzymatic Synthesis of Lipophilic Esters of Phenolic Compounds, Evaluation of Their Antioxidant Activity and Effect on the Oxidative Stability of Selected Oils

The aim of the study was to compare the effect of the substituent and its position in the aromatic ring on the antioxidant activity of hexanoic acid esters obtained in reactions catalyzed by immobilized lipase B from Candida antarctica. 4-Hydroxybenzyl hexanoate, 2-hydroxybenzyl hexanoate, 4-methoxybenzyl hexanoate, and vanillyl hexanoate were obtained with conversion yields of 50 to 80%. The antioxidant activity of synthesized esters, their alcohol precursors and BHT (Butylated HydroxyToluene) was compared with DPPH (2,2-diphenyl-1-picrylhydrazyl), CUPRAC (cupric ion reducing antioxidant capacity), and CBA (crocin bleaching assay) methods. Furthermore, it was investigated whether the presence of vanillyl hexanoate in a concentration of 0.01 and 0.1% affected the oxidative stability of sunflower and rapeseed oils in the Rancimat test. It was observed that the antioxidant activity of hexanoic acid esters depends on the presence and position of the hydroxyl group in the aromatic ring. The highest activities were found for vanillyl alcohol, vanillyl hexanoate, and BHT. The addition of the ester and BHT significantly extended the induction times of the tested oils, and these compounds exhibited similar activity. Vanillyl hexanoate increased the induction time from 4.49 to 5.28 h and from 2.73 to 3.12 h in the case of rapeseed and sunflower oils, respectively.

Sustainable synthesis of vanillin through base-free selective oxidation using synergistic AgPd nanoparticles loaded on ZrO2

Sustainable synthesis of vanillin was realized over a synergistic AgPd/ZrO2 catalyst through the base-free selective oxidation of vanillyl alcohol.