Isolation from wheat plant extracts

To date, the structural features of pectic polysaccharides and plant cell walls have been studied extensively using chemical analysis and enzymatic degradation. In addition, research on isolation and physicochemical characterisation of pectin from citrus peels, apple peels, sunflower head residues and sugar beet pulp has been reported (2). However, the pectic polysaccharides extracted from wheat straw have only previously been reported by Przeszlakowska (3). The author extracted 0.44% pectic substances from Author to whom correspondence should be addressed. 

Pectins were extracted from isolated cell walls of 5-week-old wheat plants using different methods. Enzymic digestions of the cell walls involved pectinases such as a commercial pectolayse or recombinant endopolygalacturonase [Maness Mort, 1989]. Chemical extractions involved the chelating agent imidazole [Mort et al., 1991] or solvolysis with anhydrous HF at 0 °C in a closed teflon line [Mort et al., 1989] followed by imidazole extraction. 

DIBOA was also found in aqueous extracts of rye pollen [64] and it was identified as a component of root exudates from rye (0.7 - 25 pmol / kg fresh weight). However, DIBOA contents in rye exudates differ considerably depending on cultivars (cv. Forrajero Blaer 25 pmol / kg fr wt cv. Tetra Blaer 0.07 pmol / kg fr. wt.). Interestingly, wheat cultivars tested did exude neither DIBOA nor DIMBOA, although roots of the wheat cultivar Alifen contained similar amounts of DIBOA than present in roots of rye cultivars [175]. On the other hand, benzoxazinones have not only been isolated isolated from rye but also from wheat and com exudates [68,176]. Possibly, the developmental stage and plant fitness regulate the composition of root exudate constituents. 

Comparison of fresh and frozen immature plants. To obtain an adequate amount of field grown wheat for initial identification of compounds, plants were harvested and stored frozen prior to distillation-extraction. After identifications were confirmed a comparison was made between the volatiles from fresh and frozen tissue to determine if the compounds isolated from frozen samples were also present in fresh wheat tissue. For these comparisons immature plants (Figure 1) 20-30cm tall were harvested and macerated in a Waring blender prior to distillation-extraction. From Table II it can be seen that the... 

Seven enzyme catalyzed reactions are required for the synthesis of lysine from pyruvate and aspartate semialdehyde as illustrated in Fig. 3. However, enzymes catalyzing only the first and last of these reactions have been isolated from plants. Dihydropicolinate synthase facilitates the condensation of the precursors during a reaction which presumably proceeds in two steps. A double bond between the C-4 of the semialdehyde and the methyl carbon of pyruvate would be formed, with the loss of water, followed by spontaneous ring closure and the loss of a second molecule of water. Catalysis of this reaction in plant extracts was first demonstrated by Cheshire and Miflin (1975) using maize seedlings as the source of the enzyme. Mazelis et al. (1977) detected the enzyme in extracts obtained from six different taxonomic families of plants and partially purified the enzyme from wheat germ. Only the L isomer of aspartate semialdehyde was active as a substrate of this enzyme and strong cooperativity was noted when the concentration of pyruvate was varied. A dihydropicolinate synthase has also been isolated from carrot cells (Matthews and Widholm, 1978). 

Octacosanol is the main active componrait of policosanol and wheat gam oil. Octacosanol is a long carbon chain CH3(CH2)26CH20 4. It has a natural mixture of high molecular weight alcohols and is primarily isolated from sugar cane (Saccharum officinarum L) wax. Small quantities of octacosanol are available in the human diet through plants (mainly as a wax in the superficial layers of fruits), leaves, skins of common plants, and whole seeds. Most studies have used wheat germ oil extract or policosanol to elicit an octacosanol response. 

Plant proteins are generally not very expensive (around 0.5-l/kg for corn and wheat gluten, respectively, for protein contents ranging from SS to 75%). High quantities of these proteins are often present in coproducts of processed field crops (e.g. wheat and com gluten are coproducts of starch processing protein concentrates or isolates are obtained from oilcake after extracting oil from oil crops). Plant proteins are thus widely available and relatively easy to handle. Animal proteins are more expensive ( 2-10/kg ) than plant proteins. 

More recently Avila and Wallsgrove (1990) have shown that the antisera raised to barley ferredoxin-dependent glutamate synthase are able to inhibit the enzyme activity isolated from a range of plant sources. However, clear precipitation lines were detected only by Ouchterlony double-difiusion analysis with extracts from barley, wheat, rye, and rice. The enzyme from dicotyledonous and C4 plants appeared to have major differences in the amino acid composition from that purified from barley. 

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