Acetyldehydrorishitinol, a rishitinol-related potato stress metabolite
Leo M. AlvesRichard M. KirchnerDenise T. LodatoPatricia B. NeeJean M. ZappiaMary Lynn ChichesterJames D. StuartEdwin B. KalanJohn C Kissinger
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Spectral Analysis
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Qinguang” nectarine was used to investigate the effects of 1-MCP (an inhibitor of ethylene) on fruit firmness, (respiration), ethylene production and activity of ACC oxidase induced by exogenous ethylene during fruit ripening. The results showed that 1-MCP could restrain the loss of fruit firmness, the increase of respiration rates and ethylene production rates induced by exogenous ethylene. It postponed the appearing time of respiration and ethylene production, degraded the height of ethylene peak, but increased the height of respiration peak induced by exogenous ethylene. 1-MCP didn’t inhibit the increase of the activity of ACC oxidase induced by exogenous ethylene.
Respiration rate
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The metabolism of zetidoline, a new neuroleptic, in the rat and the dog has been studied. From the urine of rats and dogs given 5 mg/kg of [2-14C] zetidoline orally, unchanged drug and five metabolites were isolated and the structures of four of them assigned by physicochemical analysis. They are: metabolite B, 4'-hydroxy-3'-chlorophenyl zetidoline; metabolite D, zetidoline without the aryl group; metabolite E, the 6'-hydroxy-4'-beta-D-glucuronide of metabolite B, and metabolite F, the 4'-beta-D-glucuronide of metabolite B. The plasma levels of zetidoline and its metabolites after iv administration show that the drug is rapidly excreted and/or metabolized in both animal species. The plasma radioactivity in the dog consists mainly of the pharmacologically active (neuroleptic) metabolite B, whereas in the rat it consists of the more polar metabolites. After oral administration, elimination in both species occurs mostly via the kidneys. In the dog, within a 24-hr period, 6.2 +/- 0.4% of the dose is accounted for as unchanged zetidoline, 7.6 +/- 0.5% as metabolite B, 10.1 +/- 0.7% as the unidentified metabolite C, and 21.4 +/- 1.1% as metabolite F. In the rat, over the same period, zetidoline is present in traces, metabolite B accounts for 6.9 +/- 0.3% of the dose, metabolite D for 6.6 +/- 0.9%, metabolite E for 15.2 +/- 1.4%, and metabolite F for 31.7 +/- 2.2%.
Glucuronide
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Ethylene production by IAA-treated mung bean hypocotyl segments under various oxygen levels in the ambient atmosphere was examined. Rate of ethylene production was dependent upon oxygen levels, and gave a sigmoidal curve against oxygen levels. Tissue segments preincubated with IAA in low oxygen levels (1–10% O2 in N2) produced ethylene without a lag period at a rate higher than that by control tissue segments preincubated in air, when they were exposed to a high oxygen level (air, 21% O2). The effect of cycloheximide on tissue segments transferred from a low oxygen level to air was not much different from that on ethylene production by control tissue segments previously incubated in air. Incorporation of U-14C-leucine into the protein fraction by tissue segments placed in nitrogen was negligible, but that in 2% oxygen was 10 to 14% of that in air. It was concluded that oxygen was an essential factor for both the induction process of the ethylene producing system and the synthesis of ethylene, and that although synthesis of ethylene is dependent upon oxygen levels, formation of the ethylene producing system proceeded even under low oxygen levels.
Limiting oxygen concentration
Oxygene
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The fungi in the genus Isaria produce a variety of inhibitory metabolites. Typically, Isaria are known as entomopathogenic fungi. However, we have isolated a strain of this fungus that produces a metabolite that inhibits the growth of other fungi. The metabolite was produced during growth in potato dextrose broth. The filtered broth was analyzed to quantify the antifungal activity of the metabolite. Using a panel of fungal plant pathogens, we determined the minimal inhibitory concentration (MIC) of the Isaria metabolite with the XTT assay. The fungal spores of the test organisms were grown with and without the Isaria metabolite. The MIC of the metabolite was then compared to other known antifungal agents (ex. boric acid). Depending on the species tested, the metabolite demonstrated a higher or lower MIC in comparison to boric acid. TLC analysis was also done in order to identify how many (or if any) chemical components were made up of the metabolite in order to determine whether or not the metabolite was a protein or a molecule. Current studies are focused on characterizing the metabolite by examining the effects of temperature, pH, and light exposure on activity. Future studies will be concentrated on continuing to isolate and identify the metabolite.
Secondary metabolite
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In order to assess the contribution of an active metabolite to the overall pharmacological response following drug administration it is necessary to characterise the metabolite concentration-time profile. The influence of route of drug administration on metabolite kinetics has been investigated by computer simulation. Comparisons between simulated profiles and published concentration-time data have been carried out. A route dependence in metabolite concentration-time curves is readily apparent provided the metabolite kinetics are formation rate limited and the hepatic clearance of drug is greater than 25 l/h (medium to highly cleared). Oral drug administration produces a triphasic metabolite concentration-time profile whereas only two phases are discernable after intravenous drug administration. The magnitude of the difference in maximum metabolite concentration is directly proportional to the hepatic clearance of drug due to first-pass metabolite production. The route dependence in the shape of the metabolite concentration-time curves is most dramatic when the absorption and distribution of drug and the elimination of metabolite is rapid. A reduction in the rate of either of these processes alters the shape of the metabolite concentration-time profile such that the consequence of first-pass metabolite formation may be reduced.
Active metabolite
Clearance
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Active metabolite
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1. The biotransformation of prostaglandin E(1) (PGE(1)) was studied in the isolated, perfused dog kidneys.2. An average 43% of PGE(1) was converted into the less polar metabolite I by a single passage through the kidney. As the re-circulation of the perfusate continued, PGE(1) was converted not only into metabolite I but also the least polar metabolite II. The velocity of the conversion of PGE(1) into metabolite I was significantly greater than that into metabolite II. Usually, six passages elapsed before maximum degradation of PGE(1) occurred.3. Further separation with silicic acid column chromatography and gas-liquid chromatography showed that metabolite II consists of two individual metabolites, metabolite IIa and metabolite IIb.4. The present study indicates that the kidney biotransforms PGE(1) rather rapidly into three metabolites which are less polar than PGE(1).
Dinoprostone
Primary metabolite
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