J.B. Pridham

Antioxidant potential of intermediates in phenylpropanoid metabolism in higher plants

In this study the antioxidant activities of the hydroxycinnamic acids, chlorogenic, caffeic, ferulic and p‐coumaric have been investigated in peroxidising lipid systems mediated by metmyoglobin. The results show that the order of effectiveness in increasing the resistance of LDL to peroxidation, in protecting LDL cholesterol from oxidation and preventing the oxidative modification of the LDL apoprotein B100 is caffeic = chlorogenic > ferulic > p‐coumaric acid. Assessment of the rates of reaction of the hydroxycinnamates with ferrylmyoglobin, a product of the reductive decomposition of lipid hydroperoxides, reveals that the compounds are more effective as peroxyl radical scavengers than reductants of ferryl myoglobin in peroxidising LDL systems mediated by haem proteins.

The phenol glucosylation reaction in the plant kingdom

Abstract The ability of various plant tissues to convert quinol and resorcinol to the corresponding mono-β- d -glucopyranosides in vivo has been studied. This activity is prominent in the angiosperms (except for some water plants) and gymnosperms and appears to be entirely absent in the algae and fungi. The significance of these findings is discussed.

Studies on the distribution of α-galactosidases in seeds

Abstract Dormant seeds from various higher plant species have been examined for multiple forms of α-galactosidase. The properties of corresponding forms from Pisum sativum and Vicia faba have been compared. The high molecular from (I) from P. sativum has been purified 2770-fold.

Post-harvest changes in Mangifera indica mesocarp cell walls and cytoplasmic polysaccharides

Abstract During ripening, mango mesocarp cell walls undergo degradation with the net loss of arabinose, galactose and galacturonic acid. Hot water fractions of the cell walls from unripe fruits were rich in galactose and arabinose and contained only 7% galacturonic acid in comparison with those from unripe fruits which contained 90% uronic acid: little change occurred in the alkali-soluble (hemicellulose) fraction during ripening. The ripening-associated changes in the cold water-soluble cytoplasmic polysaccharides in the mesocarp were also examined. As the mesocarp softened these increased in amount and bound uronic acid increased three-fold. Gel-filtration and ion-exchange chromatography were used to examine these cytoplasmic polysaccharides. Their average M r decreased on ripening and most of the fractions were complex with respect to monosaccharide composition. However, polysaccharides which are essentially an arabinoxylan and a galacturonan appeared to be present in the unripe and ripe tissue, respectively.

Observations on the translocation of phenolic compounds

Abstract The rates of translocation of phenolic compounds introduced into the apical leaves of Vicia faba have been estimated. Some evidence for the occurrence of phenolic compounds in the sieve tubes of Salix and Vicia has been obtained using “aphid techniques”.

The lectin nature of α-galactosidases from Vicia faba seeds

α‐Galactosidase from Vicia faba seeds has been resolved into three molecular forms, I, II1 and II2, respectively. Enzyme I is a tetramer (M r 160 000) consisting of identical sub‐units (M r 44000 ± 2000). All three forms display lectin activity with glucose/mannose specificity. Enzyme I has been further studied with respect to its lectin specificity and various factors affecting this property. The results indicate that the catalytic and the lectin sites reside in the same protein molecule. The results presented are unique in that the enzyme activity is specific for galactose and its lectin activity is specific for glucose/mannose.

Can microorganisms convert antimony trioxide or potassium antimonyl tartrate to methylated stibines

No evidence could be found for the production, in culture, of methylated antimony compounds from water-insoluble or soluble antimony derivatives by the aerobes, Scopulariopsis brevicaulis or Bacillus sp. or by anaerobes associated with cot mattress materials. The study does not support the hypothesis that volatile organoantimony compounds are a cause of cot deaths. Anaerobic cultures from a polluted pond generated trimethylstibine from potassium antimonyl tartrate.

Multiple forms of Vicia faba α-galactosidases and their relationships

Abstract Three highly purified α-galactosidases, I, II 1 and II 2 have been isolated from resting Vicia faba seeds. Form I (MW 160 000) is a tetrame

Melanins from DOPA-containing plants

Abstract The melanins from plants which contain DOPA and related compounds have been examined and shown to be largely composed of the catechol-type pigment. Some indole units also appear to be present, however.

Pectic substances in cured and uncured tobacco

Abstract The structures of pectin and reduced pectin from cured leaf stems of Bright Virginia tobacco, and pectin from fresh leaves of Virginia tobacco plants, have been investigated. The “cured” pectin has an anhydrogalacturonic acid content of more than 90% and on partial hydrolysis with a pectinase preparation yielded di-, tri-, and tetra-galacturonic acids, with α-1,4-linkages. Diborane has been used to reduce the acidic polysaccharide to the corresponding galactan which has been subjected to methylation analysis. The fresh leaf pectin has a much lower anhydrouronic acid content ( ca . 20%) and unlike “cured” pectin readily yields oligosaccharides containing neutral and acidic monosaccharides on partial hydrolysis.