Mutational Analysis of a Wheat O-methyltransferase Involved in Flavonoid Metabolism

Methylated flavones, and tricin in particular, have been implicated in protecting wheat plants against a variety of biotic and abiotic stresses. Methylated flavones are produced via O-methylation of the hydroxyl groups in flavones, which is catalyzed by O-methyltransferases (OMTs). To examine the role of wheat OMT2 in methylated flavone biosynthesis and facilitate interrogation of tricin functions in wheat-environment interactions, loss-of-function mutants of OMT2 homoeologs, omt-A2 and omt-B2, were identified from a tetraploid wheat Targeting Induced Local Lesions in Genomes (TILLING) mutant population and crossed to generate the omt-A2omt-B2 double mutant. Although tricin and most other soluble phenolics did not differ in leaves and glumes of TILLING control and the omt-A2, omt-B2, and omt-A2 omt-B2 mutants, chlorogenic acid was increased in glumes of omt-A2 omt-B2 relative to TILLING control, suggesting that it might serve as a substrate for OMT2. The omt2 mutant lines showed similar growth phenotypes as well as comparable lignin deposition in cell walls of stems compared to TILLING control. These results collectively suggest that OMT2 and its close homolog OMT1 may possess overlapping activities in tricin production, with OMT1 compensating for the missing OMT2 activities in the omt2 mutant lines.

Shedding Light on the Volatile Composition of Broa, a Traditional Portuguese Maize Bread

In Portugal, maize has been used for centuries to produce an ethnic bread called broa, employing traditional maize varieties, which are preferred by the consumers in detriment of commercial hybrids. In order to evaluate the maize volatiles that can influence consumers’ acceptance of broas, twelve broas were prepared from twelve maize varieties (eleven traditional and one commercial hybrid), following a traditional recipe. All maize flours and broas were analyzed by HS-SPME-GC-MS (headspace solid-phase microextraction) and broas were appraised by a consumer sensory panel. In addition, the major soluble phenolics and total carotenoids contents were quantitated in order to evaluate their influence as precursors or inhibitors of volatile compounds. Results showed that the major volatiles detected in maize flours and broas were aldehydes and alcohols, derived from lipid oxidation, and some ketones derived from carotenoids’ oxidation. Both lipid and carotenoids’ oxidation reactions appeared to be inhibited by soluble phenolics. In contrast, phenolic compounds appeared to increase browning reactions during bread making and, consequently, the production of pyranones. Traditional samples, especially those with higher contents in pyranones and lower contents in aldehydes, were preferred by the consumer sensory panel. These findings suggest that, without awareness, consumers prefer broas prepared from traditional maize flours with higher contents in health-promoting phenolic compounds, reinforcing the importance of preserving these valuable genetic resources.

Quantifying the Inhibitory Impact of Soluble Phenolics on Carbon Mineralization from Sphagnum-rich Peatlands

The mechanisms controlling the extraordinarily slow carbon (C) mineralization rates characteristic of Sphagnum -rich peatlands (“bogs”) remain somewhat elusive, despite decades of research on this topic. Soluble phenolic compounds have been invoked as potentially significant contributors to bog peat recalcitrance due to their affinity to slow microbial metabolism and cell growth. Despite this potentially significant role, the effects of soluble phenolic compounds on bog peat C mineralization remain unclear. We analyzed this effect by manipulating the concentration of free soluble phenolics in anaerobic bog peat incubations using water-soluble polyvinylpyrrolidone (PVP), a compound that binds with and inactivates phenolics, preventing phenolic-enzyme interactions. CO 2 and CH 4 production rates (end-products of C mineralization) correlated positively with PVP concentration following Michaelis-Menten (M.M.) saturation functions. Using M.M. parameters, we determined that soluble phenolics inhibit, at minimum, 57 ± 16% of total C (CO 2 +CH 4 ) mineralization in the anaerobic incubation conditions studied. These findings are consistent with other studies that have indicated that soluble phenolics play a significant role in regulating bog peat stability in the face of decomposition.

Two galling insects (Hartigiola annulipes and Mikiola fagi), one host plant (Fagus sylvatica) – differences between leaf and gall chemical composition

Gall-inducing organisms change the chemical properties of galled organs and host plants due to the development of gall tissues that are supposed to shelter the galler and provide it with nutrients. Hartigiola annulipes and Mikiola fagi represent the gall midge family (Diptera; Cecidomyiidae). They share a host plant species, the common beech (Fagus sylvatica), whose leaves they use for galling. Their galls are single-chambered and occur on the upper side of the leaf blade. The morphologies of their galls are different, but there are a lack of studies comparing the impact of both species on the common host. Thus, this was the aim of this study. We analysed the total contents of carbon, nitrogen, soluble carbohydrates, starch, soluble phenolics and tannins in galls, galled leaves with removed galls and leaves without galls collected in two different forest stands in western Poland (a Scots pine forest with artificially-planted beech trees and a natural beech forest). The influence of the studied gallers on the leaves is species- and forest-dependent. Perhaps seasonal changes and the level of infestation are also responsible for the chemical changes. The content of soluble carbohydrates in the galls of H. annulipes reaches an optimized level and is independent of the forest type. A high infestation level by H. annulipes is manifested itself in an elevated content of total soluble phenolics and tannins in leaves, while gall tissues do not accumulate soluble phenolics. The low levels of nitrogen in the gall tissues of both gallers leads to the rejection of the nutrition hypothesis; however, M. fagi galls act as sinks for soluble carbohydrates.

Quality of Watermelon Juice Concentrated by Forward Osmosis and Conventional Processes

Watermelon (Citrullus lanatus) juice is known for its refreshing flavor, but its high perishability limits its availability throughout the year. Watermelon juice concentrate has extended shelf-life and lower transportation and storage costs, but the conventional thermal evaporation process for concentrating juice degrades the nutritional components and sensory quality of the product. Thus, in this work, a large-scale, non-thermal forward osmosis (FO) process was used to concentrate fresh watermelon juice up to 65°Brix. The FO concentrate was compared to thermal concentrate and fresh juices, and to commercially available refrigerated watermelon juices, in terms of lycopene and citrulline content, total soluble phenolics, antioxidant activity, and sensory properties. The FO concentrate had statistically similar (p < 0.05) levels of all the nutrients of interest except antioxidant activity, when compared to the thermal concentrate. The reconstituted FO concentrate maintained the same antioxidant activity as the raw source juice, which was 45% higher than that of the reconstituted thermal concentrate. Sensory results showed that reconstituted FO concentrate resulted in highly liked juice, and it outperformed the reconstituted thermal concentrate in the sensory hedonic rating. This work demonstrates the possibility to produce a high-quality watermelon juice concentrate by forward osmosis.

Anti-diabetic and Anti-hypertensive Potential of Indigenous Edible plants of Qatar

Aizoon Canariense, Cynomorium Coccineum, Glossonema Edule, and Malva Parviflora, edible desert plants from Qatar, were selected to determine levels of phenolic bioactives and potential health benefits for managing early stages of type 2 diabetes and hypertension. Aqueous extracts of C. Cocineum, contained soluble phenolics and had relatively high levels of antioxidant activity associated with α-glucosidase, α-amylase, and angiotensin- converting enzyme (ACE). G. Edule and M. Parviflora had moderate levels of anti-oxidant potential, soluble phenolics, and ACE inhibitory activity. The medicinal properties associated with C. Coccineum suggest the plant may have potential as a diet-based solution for combating, preventing, and managing the early stage of type 2 diabetes when coupled with an overall healthy life style and pharmacological management strategies.

Seasonal changes in eastern hemlock (Tsuga canadensis) foliar chemistry

Eastern hemlock (Tsuga canadensis (L.) Carrière) is an eastern North American conifer threatened by the invasive hemlock woolly adelgid (Adelges tsugae Annand). Changes in foliar terpenes and phenolics were evaluated in new (current-year growth) and mature (1-year-old growth) hemlock needles during the growing season and into plant dormancy. From April through September, foliar concentrations of nonvolatile soluble phenolics, condensed tannins, lignin, mono- and sesquiterpenes, α-pinene, camphene, isobornyl acetate, and diterpene resin were quantified. After September, additional analyses of metabolites that continued to differ significantly between new and mature foliage were carried out. Total soluble phenolic and condensed tannin concentrations in new foliage remained low relative to those of mature foliage throughout the growing season and converged in December. Lignin concentration in new foliage converged with that of mature foliage by July. Concentrations of α-pinene, camphene, isobornyl acetate, and diterpene resin in new foliage converged with those of mature foliage within 1 month of budbreak. The convergence of terpene concentrations in new and mature foliage suggests that these metabolites may play a role in herbivore defense during the peak growing season. Conversely, soluble phenolics, including condensed tannins, may defend foliage from herbivory outside of the spring growth period.

Phytochemical Profiles and Antioxidant Activity of Grasses Used in South African Traditional Medicine

Grasses are a valuable group of monocotyledonous plants, used as nourishing foods and as remedies against diseases for both humans and livestock. Phytochemical profiles of 13 medicinal grasses were quantified, using spectrophotometric methods and ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS), while the antioxidant activity was done using DPPH and ferric-reducing-power assays. The phytochemical analysis included the total soluble phenolic content, flavonoids, proanthocyanidins, iridoids and phenolic acids. Among the 13 grasses, the root methanolic extracts of Cymbopogon spp., Cymbopogon nardus and Cenchrus ciliaris contained the highest concentrations of total soluble phenolics (27–31 mg GAE/g DW) and flavonoids (4–13 mg CE/g DW). Condensed tannins and total iridoid content were highest (2.3 mg CCE/g DW and 3.2 mg HE/g DW, respectively) in Cymbopogon nardus. The most common phenolic compounds in the grass species included ρ-coumaric, ferulic, salicylic and vanillic acids. In the DPPH radical scavenging assay, the EC50 values ranged from 0.02 to 0.11 mg/mL for the different grasses. The best EC50 activity (lowest) was exhibited by Cymbopogon nardus roots (0.02 mg/mL) and inflorescences (0.04 mg/mL), Cymbopogon spp. roots (0.04 mg/mL) and Vetiveria zizanioides leaves (0.06 mg/mL). The highest ferric-reducing power was detected in the whole plant extract of Cynodon dactylon (0.085 ± 0.45; r2 = 0.898). The observed antioxidant activity in the various parts of the grasses may be due to their rich pool of phytochemicals. Thus, some of these grasses provide a source of natural antioxidants and phytochemicals that can be explored for their therapeutic purposes.