No abstract

Three onion (Allium cepa L.) cultivars were grown to maturity at five S fertility levels and analyzed for S-alk(en)yl-L-cysteine sulfoxide (ACSO) flavor precursors, γ-glutamyl peptide (γ-GP) intermediates, bulb S, pyruvic acid, and soluble solids content. ACSO concentration and composition changed with S fertility, and the response was cultivar dependent. At S treatments that induced S deficiency symptoms during active bulbing, (+)S-methyl-L-cysteine sulfoxide was the dominant flavor precursor, and the flavor pathway was a strong sink for available S. As S fertility increased to luxuriant levels, trans(+)-S-(1-propenyl)-L-cysteine sulfoxide (PRENCSO) became the dominant ACSO. (+)S-propyl-L-cysteine sulfoxide was found in low concentration relative to total ACSO at all S fertility treatments. With low S fertility, S rapidly was metabolized and low γ-GP concentrations were detected. As S fertility increased, γ-GP increased, especially γ-L-glutamyl-S-(1-propenyl)-L-cysteine sulfoxide, the penultimate compound leading to ACSO synthesis. Nearly 95% of the total bulb S could be accounted for in the measured S compounds at low S fertility. However, at the highest S treatment, only 40 % of the total bulb S could be attributed to the ACSO and γ-GP, indicating that other S compounds were significant S reservoirs in onions. Concentrations of enzymatically produced pyruvic acid (EPY) were most closely related to PRENCSO concentrations. Understanding the dynamics of flavor accumulation in onion and other vegetable Alliums will become increasing important as the food and phytomedicinal industries move toward greater product standardization and characterization.

No abstract

This study reports the evaluation of four urinary biomarkers of renal toxicity, α-glutathione-S-transferase (α-GST), μ-GST, clusterin, and renal papillary antigen-1 (RPA-1), in male Sprague-Dawley and Han-Wistar rats given cisplatin, gentamicin, or N-phenylanthranilic acid (NPAA). Kidney injury was diagnosed histopathologically, according to site/nature of renal injury, and graded for severity. The area under the receiver operating characteristic (ROC) curve was used to compare the diagnostic accuracy of each exploratory renal biomarker with traditional indicators of renal function and injury (blood urea nitrogen [BUN], serum creatinine [sCr] as well as urinary N-acetyl-β-D-glucosaminidase [NAG] and protein). These analyses showed that increased urinary α-GST was superior to BUN, sCr, and NAG for diagnosis of proximal tubular (PT) degeneration/necrosis. Paradoxically, urinary α-GST was decreased in the presence of collecting duct (CD) injury without PT injury (NPAA administration). RPA-1 demonstrated high specificity for CD injury, superior to all of the reference biomarkers. The clusterin response correlated well with tubular injury, whatever the location, particularly when regeneration was present (superior to all of the reference markers for cortical tubular regeneration). There was no conclusive evidence for the diagnostic utility of μ-GST. The data were submitted for qualification review by the European Medicines Agency and the US Food and Drug Administration. Both agencies concluded that the data justified the qualification of RPA-1 and increased the level of evidence for, and clarified the context of use of, the previously qualified clusterin for use in male rats. These biomarkers can be used in conjunction with traditional clinical chemistry markers and histopathology in Good Laboratory Practice rodent toxicology studies used to support renal safety studies in clinical trials. Qualification of α-GST must await further explanation of the differences in response to PT and CD injury.

Through a single genetic transformation in onion (Allium cepa), a crop recalcitrant to genetic transformation, we suppressed the lachrymatory factor synthase gene using RNA interference silencing in six plants. This reduced lachrymatory synthase activity by up to 1,544-fold, so that when wounded the onions produced significantly reduced levels of tear-inducing lachrymatory factor. We then confirmed, through a novel colorimetric assay, that this silencing had shifted the trans-S-1-propenyl-L-cysteine sulfoxide breakdown pathway so that more 1-propenyl sulfenic acid was converted into di-1-propenyl thiosulfinate. A consequence of this raised thiosulfinate level was a marked increase in the downstream production of a nonenzymatically produced zwiebelane isomer and other volatile sulfur compounds, di-1-propenyl disulfide and 2-mercapto-3,4-dimethyl-2,3-dihydrothiophene, which had previously been reported in trace amounts or had not been detected in onion. The consequences of this dramatic simultaneous down-and up-regulation of secondary sulfur products on the health and flavor attributes of the onion are discussed.