Meredith A. Wilkes

Techniques for Analysis of Plant Phenolic Compounds

Phenolic compounds are well-known phytochemicals found in all plants. They consist of simple phenols, benzoic and cinnamic acid, coumarins, tannins, lignins, lignans and flavonoids. Substantial developments in research focused on the extraction, identification and quantification of phenolic compounds as medicinal and/or dietary molecules have occurred over the last 25 years. Organic solvent extraction is the main method used to extract phenolics. Chemical procedures are used to detect the presence of total phenolics, while spectrophotometric and chromatographic techniques are utilized to identify and quantify individual phenolic compounds. This review addresses the application of different methodologies utilized in the analysis of phenolic compounds in plant-based products, including recent technical developments in the quantification of phenolics.

Hydroxamic acids in cereal roots inhibit the growth of take-all

Abstract 2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) was the only hydroxamic acid (Hx) found in wheat ( Triticum aestivum ) roots, whereas both DIMBOA and 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA) were present in the roots of triticale ( Triticosecale ) and rye ( Secale cereale ). The Hx content of wheat, triticale and rye roots was highest in the apices. Growth of two isolates of the fungus Gaeumannomyces graminis var. tritici ( Ggt ), which causes the root disease take-all, was inhibited when extracts prepared from triticale and rye roots were incorporated into nutrient media. Similar extracts from two cultivars of wheat did not inhibit the growth of Ggt . When Hx were incorporated individually into nutrient media, DIBOA inhibited the growth of Ggt at concentrations as low as 0.5 mM, whereas 1 mM DIMBOA was required to inhibit fungal growth. The decomposition products of DIBOA and DIMBOA, 2(3)-benzoxazolinone (BOA) and 6-methoxybenzoxazolinone (MBOA), respectively, were less potent inhibitors of Ggt growth than the corresponding parent Hx. The effects of the Hx at concentrations up to 5 mM were only fungistatic, as growth of the colonies resumed when they were transferred to Hx-free media. The inhibition of Ggt growth by extracts of triticale and rye is attributed to the presence of DIBOA.

Characteristics of Modern Triticale Quality: The Relationship Between Carbohydrate Properties, α-Amylase Activity, and Falling Number

ABSTRACT Triticale is a high-yielding cereal crop with potential to increase grain production for human consumption over the coming decades. Minimal targeted selection has been conducted to produce cultivars with α-amylase, amylose, and nonstarch polysaccharide (NSP) content appropriate for a milling market. Nevertheless, genotypic variability exists. Standard quality screening methods used for wheat, including pasting properties, falling number, and quantification of α-amylase activity were employed to assess the environmental and genotypic variability among modern triticale cultivars and to investigate the suitability of these tests for triticale. Samples of 11 triticale lines from four environments were compared with five wheat cultivars bred for various end uses. Triticale exhibited a greater range than wheat for most tested variables, and the ranges usually overlapped. Triticale exhibited higher NSP content, generally equivalent pasting properties, higher α-amylase activity, and lower falling number ...

Storage of Wheat Grains at Elevated Temperatures Increases Solubilization of Glutenin Subunits

ABSTRACT Grains of two wheat (Triticum aestivum L.) cultivars, Sunco and Sunsoft, were stored at 4°C and 30°C for 270 days to examine changes in proteins during storage. When whole meal flour extracted from the grains was analyzed using an unfractionated protein extraction procedure, no significant changes were found in protein content or SDS-PAGE profile for either cultivar in samples stored at 30°C compared with those stored at 4°C. Fractionation of the flour samples from stored grain into soluble and insoluble proteins revealed increases in soluble protein content for both cultivars stored at 30°C compared with 4°C. The soluble protein content, expressed as a percentage of the total protein, increased by 1.5% (P = 0.032) for Sunco and by 8.0 % (P = 0.158) for Sunsoft during storage at 30°C compared with those samples stored at 4°C. Analysis by SDS-PAGE and subsequent protein identification revealed that the most evident change that occurred during storage at 30°C was an increase in the content of high ...

Growth Environment Influences Grain Protein Composition and Dough Functional Properties in Three Australian Wheat Cultivars

ABSTRACT The objectives of this study were to assess how functional properties of proteins in whole meal wheat (Triticum aestivum L.) flour vary across different growth environments. Grain from three commercial Australian Hard milling wheat cultivars was analyzed from four growth locations in 2008 and from two of the corresponding cultivars and locations in 2009. The protein content of the grain, soluble and insoluble extractable protein fractions, swelling index of glutenin (SIG), glutenin-to-gliadin ratio (Glu:Gli), percent unextractable polymeric protein (%UPP), and dough properties including force at maximum resistance (Rmax) and extensibility were measured. Based on analysis of variance of aggregated data for the cultivars, growth locations, and seasons, growth environment factors made significant contributions to variability in the total grain protein, Glu:Gli ratio, %UPP, SIG, Rmax, and extensibility of the wheat flour. Variability of protein content of the soluble and insoluble extractable protein...

Effects of Soil Type and Tillage on Protein and Starch Quality in Three Related Wheat Genotypes

ABSTRACT An experiment was conducted using three related wheat (Triticum aestivum L.) genotypes grown on two different soil types (a grey vertosol and a red kandosol) using two different tillage practices (complete and zero) to test the effects of environmental influence on grain quality. Wheat grains from plants grown in each environment were milled into flour; protein and starch were analyzed. The soil type had the biggest impact on both protein and starch content, with the grains from the grey vertosol soil having higher total, insoluble, and soluble protein contents, and lower starch content and flour swelling values. When protein was analyzed using SDS-PAGE, the major difference observed between grains from the two soil types was an increased intensity of polypeptide bands corresponding to β-amylase in grains from plants grown on grey vertosol soils.

Physiological Changes in Rhizobia after Growth in Peat Extract May Be Related to Improved Desiccation Tolerance

ABSTRACT Improved survival of peat-cultured rhizobia compared to survival of liquid-cultured cells has been attributed to cellular adaptations during solid-state fermentation in moist peat. We have observed improved desiccation tolerance of Rhizobium leguminosarum bv. trifolii TA1 and Bradyrhizobium japonicum CB1809 after aerobic growth in water extracts of peat. Survival of TA1 grown in crude peat extract was 18-fold greater than that of cells grown in a defined liquid medium but was diminished when cells were grown in different-sized colloidal fractions of peat extract. Survival of CB1809 was generally better when grown in crude peat extract than in the control but was not statistically significant (P > 0.05) and was strongly dependent on peat extract concentration. Accumulation of intracellular trehalose by both TA1 and CB1809 was higher after growth in peat extract than in the defined medium control. Cells grown in water extracts of peat exhibit morphological changes similar to those observed after growth in moist peat. Electron microscopy revealed thickened plasma membranes, with an electron-dense material occupying the periplasmic space in both TA1 and CB1809. Growth in peat extract also resulted in changes to polypeptide expression in both strains, and peptide analysis by liquid chromatography-mass spectrometry indicated increased expression of stress response proteins. Our results suggest that increased capacity for desiccation tolerance in rhizobia is multifactorial, involving the accumulation of trehalose together with increased expression of proteins involved in protection of the cell envelope, repair of DNA damage, oxidative stress responses, and maintenance of stability and integrity of proteins.

Globulin Expression in Grain of Australian Hard Wheat Cultivars Is Affected by Growth Environment

ABSTRACT Our aim was to study changes in wheat proteomes across different growth locations as the first step in linking protein composition with functional changes in grains produced with commercial production systems. Soluble and insoluble proteins were extracted sequentially from grain of three commercial wheat cultivars grown at four locations in New South Wales, Australia, during a single season. Bands were separated with SDS-PAGE and identified by peptide mass fingerprinting. Quantitative changes in the electrophoretic patterns were observed mainly in the insoluble polypeptides of molecular mass 40,000–70,000 for all three cultivars grown at two of the four locations. These proteins were identified as mainly globulin and serpin isoforms, as well as triticin. Other proteins with changed expression included disease-resistance proteins, class III peroxidase, starch branching enzyme I, β-amylase, and storage proteins. Two-dimensional electrophoretic analysis was performed on two of the same wheat cultiva...