High performance liquid chromatography method for the determination of cinnamyl alcohol dehydrogenase activity in soybean roots

Lagenaria siceraria and it's bioactive constituents in carbonic anhydrase inhibition: A bioactivity guided LC-MS/MS approach

INTRODUCTION

Lagenaria siceraria, is a popular food plant among Indians, contains a large number of phenolic compounds with several medicinal benefits, mentioned in Indian System of Medicine (ISM).

OBJECTIVES

To investigate the carbonic anhydrase inhibitory potential and inhibitory mechanism of the most potent fraction of L. siceraria fruits.

MATERIALS AND METHODS

The extract and fraction of dried fruit of L. siceraria screened for their in vitro carbonic anhydrase II (bCA II) inhibitory activity. The active fraction was purified by using flash chromatography. The bioactive compounds were identified and quantified through liquid chromatography quadrupole time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS) and reverse-phase high-performance liquid chromatography (RP-HPLC). Finally, the underlying carbonic anhydrase inhibitory mechanism of the compounds was explained by enzyme kinetics and molecular docking study.

RESULTS

The LC-QTOF-MS based identification of the most active fraction revealed the presence of phenolic compounds. The results of the enzyme inhibition assay revealed that coniferyl alcohol, ferulic acid and p-Coumaric acid inhibited bCA II activity [half maximal inhibitory concentration (IC₅₀ ) value range of 80 to 250 μM) in a dose dependent manner. The kinetics study of enzyme inhibition revealed that p-Coumaric acid binds to the enzyme competitively whereas the non-competitive type of inhibition was observed for ferulic acid and coniferyl alcohol. The molecular docking study explored the interaction mechanism of phenolic compounds at the active site of bCA II.

CONCLUSION

The present research led us to conclude that, the phenolic compounds from L. siceraria serve as major contributors for carbonic anhydrase inhibition, which could play a useful role in the management of oedema, hypertension, obesity and related metabolic disorders.

Resemblance and Difference of Seedling Metabolic and Transporter Gene Expression in High Tolerance Wheat and Barley Cultivars in Response to Salinity Stress

To elucidate inter-specific similarity and difference of tolerance mechanism against salinity stress between wheat and barley, high tolerant wheat cv. Suntop and sensitive cv. Sunmate and tolerant barley cv. CM72 were hydroponically grown in a greenhouse with 100 mM NaCl. Glutathione, secondary metabolites, and genes associated with Na+ transport, defense, and detoxification were examined to discriminate the species/cultivar difference in response to salinity stress. Suntop and CM72 displayed damage to a lesser extent than in Sunmate. Compared to Sunmate, both Suntop and CM72 recorded lower electrolyte leakage and reactive oxygen species (ROS) production, higher leaf relative water content, and higher activity of PAL (phenylalanine ammonia-lyase), CAD (cinnamyl alcohol dehydrogenase), PPO (polyphenol oxidase), SKDH (shikimate dehydrogenase), and more abundance of their mRNA under salinity stress. The expression of HKT1, HKT2, salt overly sensitive (SOS)1, AKT1, and NHX1 was upregulated in CM72 and Suntop, while downregulated in Sunmate. The transcription factor WRKY 10 was significantly induced in Suntop but suppressed in CM72 and Sunmate. Higher oxidized glutathione (GSSG) content was accumulated in cv. CM72 and Sunmate, but increased glutathione (GSH) content and the ratio of GSH/GSSG were observed in leaves and roots of Suntop under salinity stress. In conclusion, glutathione homeostasis and upregulation of the TaWRKY10 transcription factor played a more important role in wheat salt-tolerant cv. Suntop, which was different from barley cv. CM72 tolerance to salinity stress. This new finding could help in developing salinity tolerance in wheat and barley cultivars.

Exogenous application of rosmarinic acid improves saccharification without affecting growth and lignification of maize

Biomimetically incorporated into the lignin structure, rosmarinic acid improves in vitro maize cell wall saccharification; however, no in planta studies have been performed. We hypothesized that rosmarinic acid, itself, could inducer saccharification without disturbing plant growth. Its effects on growth, enzymes of the phenylpropanoid pathway, lignin, monomeric composition, and saccharification of maize were evaluated. In a short-term (24 h) exposure, rosmarinic acid caused deleterious effects on maize roots, inhibiting the first enzymes of the phenylpropanoid pathway, phenylalanine ammonia-lyase and tyrosine ammonia-lyase, altering lignin composition and slightly increasing saccharification. In a long-term (14 d) exposure, rosmarinic acid increased saccharification of maize stems by about 50% without any deleterious effects on plant growth, the phenylpropanoid pathway and lignin formation. This demonstrated that exogenous application of rosmarinic acid on maize plants improved saccharification, and represented an interesting approach in facilitating enzymatic hydrolysis of biomass polysaccharides and increasing bioethanol production.

Optimization of an Ultrasound-Assisted Extraction for Simultaneous Determination of Antioxidants in Sesame with Response Surface Methodology

Sesame is a nutritional agricultural product with medicinal properties. Accurate determination of micronutrients is important for the improvement of sesame quality and nutrition assessments. Our previous study showed that 10 antioxidants—d-homoproline, vitamin B₂, coniferyl aldehyde, hesperidin, phloretin, N-acetyl-l-leucine, l-hyoscyamine, ferulic acid, 5-methoxypsoralen, and 8-methoxypsoralen—in sesame were potential characteristic nutrients in sesame. Herein, simultaneous detection of 10 different types of antioxidants was developed by using ultrasound-assisted extraction coupled with liquid chromatography-tandem mass spectrometry (UAE-LC-MS/MS) with the help of response surface methodology. The significant variables and levels were screened and optimized by combining the single factor experiment, Plackett–Burman test, and Box–Behnken design. The optimal conditions for extraction of target antioxidants in sesame were methanol solution of 75.0%, liquid-to-material ratio of 20:1 (mL/g), extraction temperature of 50 °C, extraction power of 410.0 W, extraction time of 65 min. The total yield of targets was 21.74 μg/g under the optimized conditions. The mobile phase used was 0.1% formic acid in acetonitrile and 0.1% formic acid in water, and the column was a Thermo Syncronis C18 reverse phase column (100 mm × 2.1 mm, 3 μm). All targets required only one injection and could be quickly separated and assayed within 7 min. The limits of detection and limits of quantification for these 10 nutritional compounds ranged from 0.01 to 0.11 µg/kg and from 0.04 to 0.34 µg/kg, respectively. The validation results indicated that the method had reasonable linearity (R² ≥ 0.9990), good recoveries (71.1%–118.3%), satisfactory intra-day precision (≤9.6%) and inter-day precision (≤12.9%), and negligible matrix effects (≤13.8%). This simultaneous quantification method was accurate, fast, and robust for the assessment of sesame nutrition.

Comparative effects of L-DOPA and velvet bean seed extract on soybean lignification

Velvet bean (Mucuna pruriens) is an efficient cover forage that controls weeds, pathogens and nematodes, and the non-protein amino acid L-3,4-dihydroxyphenylalanine (L-DOPA) is its main allelochemical. The effects of 3 g L-1 of an aqueous extract of velvet bean seeds, along with 0.5 mM L-DOPA for comparison, were evaluated in roots, stems and leaves of soybean (Glycine max). The activities of phenylalanine ammonia lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) were determined, along with the lignin content and its monomeric composition. The results revealed similar effects caused by L-DOPA and the aqueous extract. Both treatments reduced PAL and CAD activities, lignin, and lignin monomer contents in roots; PAL and CAD activities in stems, and CAD activity in leaves. These findings provide further evidence that the effects of velvet bean cover forage on root lignification were due to the L-DOPA, its major allelochemical.

Transcriptome-wide identification and characterization of CAD isoforms specific for podophyllotoxin biosynthesis from Podophyllum hexandrum

Podophyllotoxin (ptox) is a therapeutically important lignan derived from Podophyllum hexandrum and is used as a precursor for the synthesis of anticancer drugs etoposide, teniposide and etopophose. In spite of its enormous economic significance, genomic information on this endangered medicinal herb is scarce. We have performed de novo transcriptome analysis of methyl jasmonate (MeJA)-treated P. hexandrum cell cultures exhibiting enhanced ptox accumulation. The results revealed the maximum up-regulation of several isoforms of cinnamyl alcohol dehydrogenase (CAD). CAD catalyzes the synthesis of coniferyl alcohol and sinapyl alcohol from coniferaldehyde (CAld) and sinapaldehyde respectively. Coniferyl alcohol can produce both lignin and lignan while sinapyl alcohol produces only lignin. To isolate the CAD isoforms favoring ptox, we deduced full length cDNA sequences of four CAD isoforms: PhCAD1, PhCAD2, PhCAD3 and PhCAD4 from the contigs of the transcriptome data. In vitro enzyme assays indicated a higher affinity for CAld over sinapaldehyde for each isoform. In silico molecular docking analyses also suggested that PhCAD3 has a higher binding preference with CAld over sinapaldehyde, followed by PhCAD4, PhCAD2, and PhCAD1, respectively. The transgenic cell cultures overexpressing these isoforms independently revealed that PhCAD3 favored the maximum accumulation of ptox as compared to lignin followed by PhCAD4 and PhCAD2, whereas, PhCAD1 favored both equally. Together, our study reveals transcriptome-wide identification and characterization of ptox specific CAD isoforms from P. hexandrum. It provides a useful resource for future research not only on the ptox biosynthetic pathway but on overall P. hexandrum, an endangered medicinal herb with immense therapeutic importance.

Ferulic acid: a key component in grass lignocellulose recalcitrance to hydrolysis

In the near future, grasses must provide most of the biomass for the production of renewable fuels. However, grass cell walls are characterized by a large quantity of hydroxycinnamic acids such as ferulic and p-coumaric acids, which are thought to reduce the biomass saccharification. Ferulic acid (FA) binds to lignin, polysaccharides and structural proteins of grass cell walls cross-linking these components. A controlled reduction of FA level or of FA cross-linkages in plants of industrial interest can improve the production of cellulosic ethanol. Here, we review the biosynthesis and roles of FA in cell wall architecture and in grass biomass recalcitrance to enzyme hydrolysis.

Elicitor-induced defense responses in Solanum lycopersicum against Ralstonia solanacearum

We investigated on important parameters of induced resistance in hydroponic tomato (Solanum lycopersicum) against Ralstonia solanacearum using the elicitors chitosan (CHT), salicylic acid (SA), and jasmonic acid (JA). The increase in total phenolic content of roots by the elicitors was significantly higher than control. Most pronounced increase in lignin synthesis was triggered by SA followed by CHT. At 24 h post-elicitation (hpe), the activity of phenylalanine ammonia lyase was 4.5 times higher than control elicited by CHT. The peroxidase activity was about 86 nkat/mg protein at 24 hpe in case of SA and 78 nkat/mg protein in case of CHT. The activity of polyphenol oxidase increased several folds by the elicitors. Cinnamyl alcohol dehydrogenase activity increased to the maximum at 48 hpe under the influence of CHT. The results indicate that the elicitors SA and CHT induced effective defense responses in tomato plants against R. solanacearum. This was evident from reduced vascular browning and wilting symptoms of tomato plants treated with SA and CHT and challenged subsequently with R. solanacearum. This reduced disease incidence in tomato by SA and CHT may be a result of cell wall strengthening through deposition of lignin and the coincident induction of defense enzymes.

Proteomic analysis of salicylic acid-induced resistance to Magnaporthe oryzae in susceptible and resistant rice

To probe salicylic acid (SA)-induced sequential events at translational level and factors associated with SA response, we conducted virulence assays and proteomic profiling analysis on rice resistant and susceptible cultivars against Magnaporthe oryzae at various time points after SA treatment. The results showed that SA significantly enhanced rice resistance against M. oryzae. Proteomic analysis of SA-treated leaves unveiled 36 differentially expressed proteins implicated in various functions, including defense, antioxidative enzymes, and signal transduction. Majority of these proteins were induced except three antioxidative enzymes, which were negatively regulated by SA. Consistent with the above findings, SA increased the level of reactive oxygen species (ROS) with resistant cultivar C101LAC showing faster response to SA and producing higher level of ROS than susceptible cultivar CO39. Furthermore, we showed that nucleoside diphosphate kinase 1, which is implicated in regulation of ROS production, was strongly induced in C101LAC but not in CO39. Taken together, the findings suggest that resistant rice cultivar might possess a more sensitive SA signaling system or effective pathway than susceptible cultivar. In addition, our results indicate that SA also coordinates other cellular activities such as photosynthesis and metabolism to facilitate defense response and recovery, highlighting the complexity of SA-induced resistance mechanisms.

Changes in cinnamyl alcohol dehydrogenase activities from sugarcane cultivars inoculated with Sporisorium scitamineum sporidia

This study describes a method for determining cinnamyl alcohol dehydrogenase activity in sugarcane stems using reverse phase (RP) high-performance liquid chromatography to elucidate their possible lignin origin. Activity is assayed using the reverse mode, the oxidation of hydroxycinnamyl alcohols into hydroxycinnamyl aldehydes. Appearance of the reaction products, coniferaldehyde and sinapaldehyde is determined by measuring absorbance at 340 and 345 nm, respectively. Disappearance of substrates, coniferyl alcohol and sinapyl alcohol is measured at 263 and 273 nm, respectively. Isocratic elution with acetonitrile:acetic acid through an RP Mediterranea sea C18 column is performed. As case examples, we have examined two different cultivars of sugarcane; My 5514 is resistant to smut, whereas B 42231 is susceptible to the pathogen. Inoculation of sugarcane stems elicits lignification and produces significant increases of coniferyl alcohol dehydrogenase (CAD) and sinapyl alcohol dehydrogenase (SAD). Production of lignin increases about 29% in the resistant cultivar and only 13% in the susceptible cultivar after inoculation compared to uninoculated plants. Our results show that the resistance of My 5514 to smut is likely derived, at least in part, to a marked increase of lignin concentration by the activation of CAD and SAD.

Significance of phenols in cadmium and nickel uptake

The effects of 2-aminoindane-2-phosphonic acid (AIP), a potent phenylalanine ammonia-lyase (PAL) inhibitor, on the accumulation of cadmium and nickel in chamomile (Matricaria chamomilla) were examined in this study. In vitro assay of AIP effect showed a 90% reduction in PAL activity. In plants cultured for 7 days in Cd or Ni solutions with AIP, PAL activity was higher in both shoots and roots (in comparison with metals without AIP), and was correlated with changes in free phenylalanine content. Individual amino acids were both positively and negatively affected by AIP, with the accumulation of tyrosine and proline showing increases in some variants. Contents of soluble phenols and flavonoids were not considerably affected, while amounts of coumarin-related compounds, cell wall-bound phenols and phenolic acids were substantially reduced in AIP-treated variants. Lignin accumulation decreased in controls and increased in Cd variants in response to AIP. Shoot Cd content was depleted, but shoot Ni was elevated by AIP. Total root content of Cd and Ni decreased in +AIP variants. AIP also caused more expressive changes in hydrogen peroxide and superoxide content in Cd than in Ni variants. Our results indicate that phenols have important roles in the uptake of Cd and Ni. The present findings are discussed in the context of available data regarding AIP's effect on phenols.

Tolerance of Silene vulgaris to copper: population-related comparison of selected physiological parameters

Tolerance of three Slovak populations of Silene vulgaris [from the localities "Harmanec" (total soil Cu 34.1 mg kg⁻¹), "Lubietová"; (total soil Cu 831.6 mg kg⁻¹) and "Špania dolina" (total soil Cu 1368.7 mg kg⁻¹) referred as SV1, SV2, and SV3, respectively] and Silene dioica (SD; from the locality "Špania dolina") exposed to 60 μM Cu for 7 days has been studied. Respective controls with 0.21 μM Cu were also cultured. SV3 and SD contained higher total shoot Cu than SV1. Methanol-soluble shoot Cu represented 60, 59, 59, and 55% from total shoot Cu and roots contained 16.7-, 20.4-, 9.9- and 28.9-fold more Cu than shoots in SV1, SV2, SV3, and SD, respectively. Soluble proteins were the least affected in SV3 and SD when Cu-exposed and control plants were compared. Root hydrogen peroxide and superoxide showed similar trend and were correlated with enhancement of ascorbate- and guaiacol-peroxidase activities. Malondialdehyde accumulation increased in SV1 and SV2. Phenylalanine ammonia-lyase activity and total soluble phenols were higher in SV3 Cu-exposed plants compared to SV1 and SV2. Shikimate dehydrogenase activity was enhanced in all Cu-exposed populations. Cinnamyl alcohol dehydrogenase activity and root lignin content were not affected and polyphenol oxidase activity was not detected. Within 14 detected free amino acids, majority of them decreased preferentially in the roots. Only serine increased in shoots and decreased in roots of all populations. Potassium content was not affected in SV3. Na, Ca, and Fe increased in roots of Cu-exposed plants of all populations, while Mg was the least affected and Zn increased in SV2 and SV3 shoots and roots. This study revealed the highest tolerance in population from the locality with the highest soil Cu content. Present findings as complex metabolic responses to Cu stress with special emphasis on phenolic metabolism are discussed.

Phenolic metabolism of Matricaria chamomilla plants exposed to nickel

We examined accumulation of phenolic acids, total soluble phenolics and flavonoids, and activities of phenolic metabolism-related enzymes (shikimate dehydrogenase (SKDH), phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), polyphenol oxidase (PPO)) in Matricaria chamomilla plants exposed to 3, 60 and 120 microM of nickel (Ni) for 10 days. Ni showed low toxicity as indicated by unaltered content of total soluble phenolics in the leaf rosettes. In the roots, the effects of Ni were more visible, including increased total phenolics and PAL activity, but a decrease in PPO activity was observed. CAD activity was not affected by any of the Ni concentrations. Cinnamic acid derivatives were affected more than benzoic acid derivatives. Accumulation of chlorogenic acid, an important antioxidant compound, was enhanced by Ni treatment (ca. 4-fold in 120 microM Ni). Accumulation of protocatechuic acid, a phenol with high chelating strength, even decreased in the leaf rosettes. These observations are discussed in connection to antioxidative properties of phenolic metabolites and previously tested metals (cadmium and copper).

Salicylic acid alleviates NaCl-induced changes in the metabolism of Matricaria chamomilla plants

Influence of 100 mM NaCl and 50 microM salicylic acid (SA) and their combination on the metabolism of chamomile (Matricaria chamomilla) during 7 days was studied. NaCl reduced growth and selected physiological parameters and SA in combined treatment (NaCl + SA) reversed majority of these symptoms. Application of SA reduced NaCl-induced increase of Na+ in the rosettes, but not in the roots. Accumulation of total amino acids was stimulated in NaCl-treated roots, especially due to exceptional increase of proline (4.4-fold). Among phenolic acids, accumulation of protocatechuic acid was the most enhanced in NaCl-exposed leaf rosettes (ca. 3-fold) while chlorogenic and caffeic acids in the roots (2.4- and 2.8-fold, respectively). Total soluble phenols increased after NaCl and SA treatments, but root lignin content was not affected. Activity of phenylalanine ammonia-lyase and shikimate dehydrogenase increased in response to NaCl, but cinnamyl alcohol dehydrogenase was not affected and polyphenol oxidase decreased. Stress parameters were elevated by NaCl treatment (superoxide radical and malondialdehyde content, activities of catalase, ascorbate- and guaiacol-peroxidase) and substantially prevented by SA, while accumulation of hydrogen peroxide decreased. Overall, SA showed strong beneficial properties against NaCl-induced negative symptoms. Protective effect of SA was the most visible at the level of guaiacol-peroxidase and through amelioration of stress parameters and mineral nutrient contents.

Nitric oxide signals ROS scavenger-mediated enhancement of PAL activity in nitrogen-deficient Matricaria chamomilla roots: side effects of scavengers

Owing to the abundance of phenolic metabolites in plant tissue, their accumulation represents an important tool for stress protection. However, the regulation of phenolic metabolism is still poorly known. The regulatory role of reactive oxygen species (ROS) in the activity of phenylalanine ammonia-lyase (PAL) in nitrogen (N)-deficient chamomile roots treated for 24 h was studied using three ROS scavengers [dithiothreitol (DTT), salicylhydroxamic acid, and sodium benzoate]. Scavengers decreased the level of hydrogen peroxide and/or superoxide (and up-regulated ascorbate/guaiacol peroxidase and glutathione reductase), but, surprisingly, stimulated PAL activity. This up-regulation was correlated with increases in nitric oxide (NO) content, total soluble phenols, selected phenolic acids, and, partially, lignin (being expressed the most in DTT-exposed roots). We therefore tested the hypothesis that NO may be involved in these changes. Application of 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) decreased PAL activity and the accumulation of soluble phenols in all treatments. Exogenous H(2)O(2) and NO also stimulated PAL activity and the accumulation of phenols. We conclude that NO, in addition to hydrogen peroxide, may regulate PAL activity during N deficiency. The anomalous effect of PTIO on NO content and possible mechanism of ROS scavenger-evoked NO increases in light of the current knowledge are also discussed.

Soybean (Glycine max) root lignification induced by ferulic acid. The possible mode of action

Ferulic acid, in the form of feruloyl CoA, occupies a central position as an intermediate in the phenylpropanoid pathway. Due to the allelopathic function, its effects were tested on root growth, H(2)O(2) and lignin contents, and activities of cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) and peroxidase (POD, EC 1.11.1.7) from soybean (Glycine max (L.) Merr.) root seedlings. Three-day-old seedlings were cultivated in half-strength Hoagland's solution (pH 6.0), with or without 1.0 mM ferulic acid in a growth chamber (25 degrees C, 12/12 hr light/dark photoperiod, irradiance of 280 micromol m(-2) s(-1)) for 24 or 48 hr. Exogenously supplied ferulic acid induced premature cessation of root growth, with disintegration of the root cap, compression of cells in the quiescent center, increase of the vascular cylinder diameter, and earlier lignification of the metaxylem. Moreover, the allelochemical decreased CAD activity and H(2)O(2) level and increased the anionic isoform PODa5 activity and lignin content. The lignin monomer composition of ferulic acid-exposed roots revealed a significant increase of guaiacyl (G) units. When applied jointly with piperonylic acid (an inhibitor of the cinnamate 4-hydroxylase, C4H), ferulic acid increased lignin content. By contrast, the application of 3,4-(methylenedioxy) cinnamic acid (an inhibitor of the 4-coumarate:CoA ligase, 4CL) with ferulic acid did not. Taken together, these results suggest that ferulic acid may be channeled into the phenylpropanoid pathway (by the 4CL reaction) and, further, may increase the lignin monomer amount solidifying the cell wall and restricting the root growth.