Nigel Deighton

Antioxidant properties of domesticated and wild Rubus species.

The antioxidative capacities of a number of Rubus species of varied pigmentation have been investigated. In addition, total phenol, anthocyanin and ascorbic acid contents have been determined. Two methods to assess the antioxidant potential of fruit juices have been used. The antioxidant capacities of the fruit ranged from 0 to 25.3 mmol Trolox equivalents g ˇ1 (TEAC) or from 190 to 66000 mmol l ˇ1 ferric reducing antioxidant power (FRAP). Ascorbic acid contributes only minimally to the antioxidant potential of Rubus juices (<10%, TEAC). There are apparent linear relationships between antioxidant capacity (assessed as both TEAC and FRAP) and total phenols (r xy = 0.6713 and 0.9646 respectively). Also, anthocyanin content has a minor influence on antioxidant capacity (r xy = 0.3774, TEAC; r xy =0.5883, FRAP). The sample with the highest antioxidant capacity (Rubus caucasicus) had the highest phenol content, but only a low percentage was represented by antho- cyanins. The present study demonstrates the potential of certain wild Rubus species, notably R caucasicus, for improvement of nutritional value through germplasm enhancement programmes. # 2000 Society of Chemical Industry

Identification of glucosinolates on the leaf surface of plants from the Cruciferae and other closely related species.

Leaf-surface extracts prepared from 18 non-cultivated (wild) plant species, derived from the Capparidaceae, Cruciferae, Resedaceae and Tropaeolaceae were ranked for their ability to stimulate oviposition by the cabbage root fly, and analysed for glucosinolates. A total of 28 different glucosinolates were identified. A clear relationship was detected between the indolyl-, benzyl- and the total glucosinolate composition on the leaf surface and oviposition preference by cabbage root fly females. However, as the results are not fully explained by differences in leaf surface glucosinolates, other important oviposition deterrents and stimuli on the leaf surface of these wild crucifers must also be present.

Botrydial is produced in plant tissues infected by Botrytis cinerea.

The fungal metabolite botrydial was detected for the first time in ripe fruits of sweet pepper (Capsicum annuum) wound-inoculated with conidial suspensions of Botrytis cinerea and also in leaves of Phaseolus vulgaris and Arabidopsis thaliana inoculated without wounding. This phytotoxin was produced in soft rot regions of the infection. In C. annuum, the most aggressive isolate produced the highest botrydial concentrations in planta. The levels of botrydial produced by this isolate did not correlate with the reported relative susceptibilities of four P. vulgaris genotypes. The results suggest that botrydial is a pathogenicity factor for this fungus, but not a primary determinant of pathogenicity.

Quantitative trait transcripts for nicotine resistance in Drosophila melanogaster

Although most genetic association studies are performed with the intention of detecting nucleotide polymorphisms that are correlated with a complex trait, transcript abundance should also be expected to associate with diseases or phenotypes. We performed a scan for such quantitative trait transcripts in adult female heads of the fruit fly (Drosophila melanogaster) that might explain variation for nicotine resistance. The strongest association was seen for abundance of ornithine aminotransferase transcripts, implicating detoxification and neurotransmitter biosynthesis as mediators of the quantitative response to the drug. Subsequently, genetic analysis and metabolite profiling confirmed a complex role for ornithine and GABA levels in modification of survival time upon chronic nicotine exposure. Differences between populations from North Carolina and California suggest that the resistance mechanism may be an evolved response to environmental exposure.

Plasma and urinary phyto-oestrogens as biomarkers of intake: validation by duplicate diet analysis

Estimating intake of phyto-oestrogens (PO) is difficult because there is inadequate information on the PO content of foods. Development of a biomarker of intake is therefore necessary for carrying out epidemiological studies. We aimed to validate a newly constructed PO database, containing more than 600 values assigned to foods by using duplicate diet analysis, and to investigate the relationships between measured PO intake, urinary excretion and plasma concentrations of PO. Fourteen subjects with estimated dietary intakes of PO ranging from 0 to 44 mg/d, measured by 7 d weighed intake, completed a duplicate diet collection over 24 h. Concurrently, a 24 h urine collection, validated using p-aminobenzoic acid, was obtained and one timed spot plasma sample taken. Duplicate diets, complete urine collections and plasma samples were analysed for total genistein and daidzein using liquid chromatography-MS to determine PO intake. The potential for 24 h urinary excretion and plasma PO concentrations to reflect dietary intake was investigated. Mean estimated and measured dietary PO intakes were 12.3 and 11.0 mg/d respectively. The correlation between estimated intake and measured intake of PO was highly significant (r 0.98, P<0.001). Urinary excretion (24 h) and plasma concentrations of PO were significantly related to measured dietary PO intake (r 0.97, P<0.001 and r 0.92, P<0.001 respectively). The relationship between 24 h urinary PO excretion and timed plasma concentrations was also significant (r 0.99, P<0.001). These findings validate the PO database and indicate that 24 h urinary excretion and timed plasma concentrations can be used as biomarkers of PO intake.

Markers for oxidative stress associated with soft rots in French beans (Phaseolus vulgaris) infected by Botrytis cinerea

Abstract. The role of active oxygen species has been studied in spreading soft-rot lesions caused by the necrotrophic fungal pathogen Botrytis cinerea Pers.:Fr. in leaves of four genotypes of French bean (Phaseolus vulgaris L.). Large increases were observed for the aldehydic end-products of oxidative damage, malondialdehyde and 4-hydroxy-2-nonenal, as a result of infection in each of the genotypes studied. Similar increases were found in a stable free radical and g=4.27 Fe(III) signals, but not Mn(II) signals, in electron paramagnetic resonance spectra. These changes were accompanied by large decreases in ascorbic acid levels, with changes in the antioxidant glutathione being genotype dependent.

Systems Genomics of Metabolic Phenotypes in Wild-Type Drosophila melanogaster

Systems biology is an approach to dissection of complex traits that explicitly recognizes the impact of genetic, physiological, and environmental interactions in the generation of phenotypic variation. We describe comprehensive transcriptional and metabolic profiling in Drosophila melanogaster across four diets, finding little overlap in modular architecture. Genotype and genotype-by-diet interactions are a major component of transcriptional variation (24 and 5.3% of the total variation, respectively) while there were no main effects of diet (<1%). Genotype was also a major contributor to metabolomic variation (16%), but in contrast to the transcriptome, diet had a large effect (9%) and the interaction effect was minor (2%) for the metabolome. Yet specific principal components of these molecular phenotypes measured in larvae are strongly correlated with particular metabolic syndrome-like phenotypes such as pupal weight, larval sugar content and triglyceride content, development time, and cardiac arrhythmia in adults. The second principal component of the metabolomic profile is especially informative across these traits with glycine identified as a key loading variable. To further relate this physiological variability to genotypic polymorphism, we performed evolve-and-resequence experiments, finding rapid and replicated changes in gene frequency across hundreds of loci that are specific to each diet. Adaptation to diet is thus highly polygenic. However, loci differentially transcribed across diet or previously identified by RNAi knockdown or expression QTL analysis were not the loci responding to dietary selection. Therefore, loci that respond to the selective pressures of diet cannot be readily predicted a priori from functional analyses.

Analysis of phospholipid molecular species by liquid chromatography--atmospheric pressure chemical ionisation mass spectrometry of diacylglycerol nicotinates.

A method using liquid chromatography - atmospheric pressure chemical ionisation mass spectrometry was evaluated for determining the molecular species composition of phospholipids (phosphatidylcholines from soybean, egg yolk and bovine liver) after conversion to diacylglycerol nicotinate derivatives. The structures could be deduced from pseudo-molecular ions ([MH-123](+)) and three pairs of monoacyl containing fragment ions. All molecular species in mixed peaks were readily identified and many minor components, earlier not encountered in the samples under investigation, were identified. Acyl chain regioisomers were readily distinguished by the ratio of the [MH-RCHCO](+) ions. Molecular species differing only in the position of the double bonds in one polyunsaturated acyl chain were separated on the basis of retention times. A half quantitative estimation of the molecular species composition of complex samples was achieved by a combination of UV detection and, for mixed peaks, the areas of [MH-123](+) ions.

Malondialdehyde and 4-hydroxy-2-nonenal in plant tissue cultures : LC-MS determination of 2, 4-dinitrophenylhydrazone derivatives

The cytologically active secondary lipid peroxidation products, malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE) have been detected as their 2,4-dinitrophenylhydrazone (DNP) derivatives in plant tissue cultures using LC-MS. This paper reports, for the first time, the use of LC-MS methodology to definitively identify 4-hydroxy-2-nonenal in plants. Limits of detection for the two derivatives are approximately 5 pmol (1.2 x 10(-9) g; 1 microM) and 0.1 pmol (3 x 10(-11) g; 20 nM) respectively. Mass spectrometer response was linear in the range from 2-200 microM DNP-MDA and 0.02-10 microM DNP-HNE. This methodology has been used to assess the formation of aldehydic secondary lipid peroxidation products in dedifferentiated callus cultures of Daucus carota. The finding that profiles of MDA and HNE can be correlated with embryogenic competence is of considerable interest as oxidative status has already been implicated as a regulatory factor in animal development.

Evaluation of liquid chromatography–atmospheric pressure chemical ionisation–mass spectrometry for the identification and quantification of desulphoglucosinolates

The use of liquid chromatography–atmospheric pressure chemical ionisation–mass spectrometry has been investigated as a potential method for both the identification and quantification of desulphoglucosinolates. The results indicate that this methodology is particularly useful as a rapid technique for the confirmation of the identity of desulphoglucosinolates and has, in full scan mode, limits of detection at least an order of magnitude lower than is normally achieved by conventional high pressure liquid chromatography with UV detection. It has been demonstrated that, using a per-deuterated desulphoglucosinolate as an internal standard, quantification could be achieved, but for accurate analysis at low concentrations it would be necessary to produce independent calibration curves for each desulphoglucosinolate present in the sample. Copyright