Robert J. Pryce

The production of resveratrol and the viniferins by grapevines in response to ultraviolet irradiation

Abstract The biosynthesis of resveratrol and the viniferins by grapevines in response to UV-irradiation has been studied. The action spectrum for the UV-irradiation induced production of resveratrol shows a maximum in the region 260–270 nm. This suggests that DNA is the photoreceptor for the response. It also provides an explanation for the fact that sunlight does not act as an inducer under field conditions. The results of feeding radiolabelled precursors are consistent with the proposal that resveratrol, in common with other plant stilbenes,is biosynthesised by the phenylalanine-polymalonate pathway. Direct evidence that resveratrol is the precursor of the viniferins was not obtained, but indirect evidence from time course studies and from biomimetic studies suggests that this is likely.

Identification of pterostilbene as a phytoalexin from Vitis vinifera leaves

Abstract An inducible antifungal compound in grapevine leaves (Vitis vinifera L., cv Cabernet-Sauvignon) has been identified as trans-pterostilbene (3,5-dimethoxy-4′-hydroxy stilbene). It is only a minor component of the phytoalexin response of V. vinifera but its antifungal activity is relatively high by comparison with resveratrol and the viniferins, stress metabolites which have been identified previously in grapevine. Methods for the quantitative analysis of pterostilbene, resveratrol, e- and α-viniferins by HPLC are described.

Isolation and characterization of two phytoalexins from rice as momilactones A and B

Abstract Two phytoalexins were isolated as chromatographically homogeneous amorphous solids from UV-irradiated, dark-grown rice coleoptiles. From their mass and 1 H NMR spectra, the compounds were characterized as the known diterpenes, momilactones A and B. The same compounds were also produced in blast-infected, WL 28325-treated rice leaves. They appear to be the first clearly identified cereal phytoalexins.

Two novel stilbene phytoalexins from Arachis hypogaea

Abstract Three phytoalexins were isolated from groundnut seeds which had been sliced and incubated for 48 hr at 25†. Two were novel isoprenylated stilbene der

Isolation from atelia herbert-smithii pittier (sophoreae, leguminosae) and x-ray structure of cis-1-amino-3-hydroxymethyl-cyclobutane-1-carboxylic acid, an achiral non-protein amino acid

Abstract barcis -1-Amino-3-hydroxymethyl-cyclobutane-1-carboxylic Acid (1) has been isolated from Atelia herbert-smithii Pittier (Leguminosae) and its structure determined by spectroscopic and X-ray crystallographic methods. By a study of the 1H NMR spectrum of the crude extract, the relative amount of (I) to that of methanoproline in the plant was shown to be 1 to 1.15.

Decomposition of aqueous solutions of gibberellic acid on autoclaving

Abstract A qualitative and quantitative analysis of the decomposition of unbuffered and buffered (pH 3–8) aqueous solutions of gibberellic acid (GA 3 ) on autoclaving is recorded. The identified products, which vary in composition with pH, are iso -GA 3 (II), iso -GA 3 hydroxy acid (III), gibberellenic acid (IV), allogibberic acid (V), epiallogibbe detected after autoclaving in all cases. The identified products, in all cases, account for not less than 95% of the decomposition product, Dehydroallogibberic acid has not previously been recorded as an aqueous decomposition product of GA 3 and its biological activity in the lettuce hypocotyl test is recorded.

Oxidative dimerisation of 4-hydroxystilbenes in vitro: production of a grapevine phytoalexin mimic

Dimerisation of trans-4-hydroxystilbenes with horseradish peroxidase–hydrogen peroxide gives analogous products to those formed from phenylpropenoids; the product (IX) obtained from trans-resveratrol is structurally related to the phytoalexin (I) isolated from grapevines but the coupling orientation is different, and both the natural and synthetic dimers of resveratrol have a similar spectrum of antifungal activity.

Dihydroconiferyl alcohol - A cell division factor from Acer species.

A compound that stimulated growth of soybean callus was isolated from spring sap of sycamore (Acer pseudoplatanus L.). Insufficient compound was isolated to permit it to be characterised. A compound with identical properties was isolated from commercial maple syrup, the concentrated spring sap of Acer saccharum L. The compound was identified as 3-(3-methoxy-4-hydroxyphenyl)-propan-1-ol (dihydroconiferyl alcohol, DCA). DCA was also active in the tobacco callus and radish leaf senescence assays, but was inactive in four other tests for cytokinin activity. DCA acted synergistically with kinetin to promote soybean callus growth. It is concluded that DCA has properties distinct from those of purine cytokinins.

Microgels as soluble enzyme supports in organic media

Abstract The enzymes α-chymotrypsin, sulfatase, and esterase have been conjugated to soluble carboxyl-bearing microgels with a water-soluble carbodiimide. Enzymatic activity towards several substrates has been observed in mixed aqueous-organic and organic solvents. Michaelis-Menten parameters for the enzyme-polymer conjugates have been determined and are compare with the results from native enzyme preparations in water and enzymes immobilized on insoluble supports.

Lunularic acid decarboxylase from the liverwort Conocephalum conicum

Abstract Some properties of a preparation of an enzyme, lunularic acid decarboxylase, from the liverwort Conocephalum conicum are described. The enzyme is normally bound and could be solubilized with Triton X-100; at least some of the bound decarboxylase activity appears to be associated with chloroplasts. For lunularic acid the enzyme has K m 8.7 × 10 −5 M (pH 7.8 and 30°). Some substrate analogues have been tested but no other substrate was found. Pinosylvic acid is a competitive inhibitor for the enzyme, K i 1.2 × 10 −4 M (pH 7.8 and 30°). No product inhibition was observed. Lunularic acid decarboxylase activity has also been observed with a cell-free system from Lunularia cruciata .