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51.
Lipid and Phenolic Constituents from Seeds of Hypericum perforatum L. and Hypericum tetrapterum Fr. and their Antioxidant Activity 下载免费PDF全文
Miriam Heinrich Peter Lorenz Rolf Daniels Florian C. Stintzing Dietmar R. Kammerer 《化学与生物多样性》2017,14(8)
Seeds of Hypericum perforatum and H. tetrapterum were extracted with dichloromethane and methanol and investigated by chromatographic and mass spectrometric methods. Both species yielded a fatty oil fraction amounting to 30.5% and 18.0% of the seed weight, respectively. Linoleic acid (C18:2n‐6) was shown to be the predominant fatty acid constituent. Moreover, xanthone derivatives, i.e. tetrahydroxyxanthones (THX), xanthone‐glycosides and xanthone‐sulfonates, were assigned in methanolic extracts. For structure elucidation, one representative xanthone, namely 1,3,6,7‐THX, was synthesized and analyzed via HPLC‐DAD/MSn and GC/MS. Total THX contents were quantitated applying a validated HPLC‐DAD method, resulting in 1.25 g/kg (H. perforatum) and 0.27 g/kg (H. tetrapterum), respectively. Moreover, the free radical scavenging capacity of the methanol extracts was tested using the DPPH antioxidant assay. Both, H. perforatum (IC50 = 8.7 mg/l) and 1,3,6,7‐THX (IC50 = 3.0 mg/l), exhibited good DPPH free radical scavenging activity compared to Trolox (IC50 = 6.6 mg/l). 相似文献
52.
H. Kaltwasser 《Journal of bacteriology》1971,107(3):780-786
Bacillus fastidiosus was grown in a minimal medium that contained uric acid or allantoin, aerated by vigorous stirring. A constant, optimum pH of 7.4 was maintained by controlled addition of sulfuric acid. Washed cells converted both urate and allantoin into carbon dioxide and ammonia, simultaneously assimilating part of the available carbon and nitrogen. Urate oxidase (formerly called uricase) was present in extracts from urate-grown but not allantoin-grown cells. The formation of urate oxidase was apparently induced by urate. Urea was detected as an intermediate in some but not all of these experiments. However, the high urease activity observed in cell-free extracts may have prevented accumulation of urea in many of the experiments. The presence of glyoxylate carboligase and tartronic semialdehyde reductase activities indicates that the glycerate pathway may be involved in urate and allantoin catabolism in this organism. 相似文献
53.
Purification of a bovine liver S6 kinase 总被引:12,自引:0,他引:12
D Tabarini A Garcia de Herreros J Heinrich O M Rosen 《Biochemical and biophysical research communications》1987,144(2):891-899
A bovine liver protein serine kinase that catalyzes the multisite phosphorylation of ribosomal protein S6 has been purified to near homogeneity. The enzyme has an Mr of 67,000 on SDS-polyacrylamide gel electrophoresis and an apparent molecular weight of 55,000 on glycerol gradient sedimentation. Its enzymic properties, substrate specificity, molecular size and chromatographic behaviour are similar to those of the principal growth factor--and phorbol 12-myristate 13-acetate-stimulated S6 kinase of cultured cells. 相似文献
54.
Recent discovery of 5-hydroxymethylcytosine (5hmC) in genomic DNA raises the question how this sixth base is recognized by cellular proteins. In contrast to the methyl-CpG binding domain (MBD) of MeCP2, we found that the SRA domain of Uhrf1, an essential factor in DNA maintenance methylation, binds 5hmC and 5-methylcytosine containing substrates with similar affinity. Based on the co-crystal structure, we performed molecular dynamics simulations of the SRA:DNA complex with the flipped cytosine base carrying either of these epigenetic modifications. Our data indicate that the SRA binding pocket can accommodate 5hmC and stabilizes the flipped base by hydrogen bond formation with the hydroxyl group. 相似文献
55.
Gas exchange and abscisic acid content of Digitalis lanata EHRH. have been examined at different levels of plant water stress. Net photosynthesis, transpiration and conductance of attached leaves declined rapidly at first, then more slowly following the withholding of irrigation. The intercellular partial pressure of CO2 decreased slightly. The concentration of 2-cis(S)ABA increased about eight-fold in the leaves of non-irrigated plants as compared with well-watered controls. A close linear correlation was found between the ABA content of the leaves and their conductance on a leaf area basis. In contrast, the plot of net assimilation versus ABA concentration was curvilinear, leading to an increased efficiency of water use during stress. After rewatering, photosynthesis reached control values earlier than transpiration, leaf conductance and ABA content. From these data it is concluded that transpiration through the stomata is directly controlled by the ABA content, whereas net photosynthesis is influenced additionally by other factors.Possible reasons for the responses of photosynthesis and water use efficiency to different stress and ABA levels are discussed.Abbreviations A
net CO2 assimilation
- ABA
abscisic acid
- Ci
intercellular CO2 concentration
- g
stomatal conductance
- T
transpiration
- WUE
water use efficiency 相似文献
56.
57.
The effect of indomethacin (IND) on glucagon-induced hepatic glucose production (HGP) was studied in the isolated perfused livers of rats. Addition of IND (0.2 mM) to the perfusion medium had no effect on glucagon-stimulated HGP when compared to control experiments without added IND (1.02 +/- 0.17 vs. 1.00 +/- 0.26 mmol per (120 min X 100 g b.w.), respectively; NS). Intravenous pretreatment with both, IND (10 mg/kg b.w.), or vehicle resulted in a reduction in glucagon-induced HGP due to a decrease in hepatic glycogen content. A complete depletion of the hepatic glycogen pool and thus a lack in glucagon-stimulated HGP was observed when IND was given intraperitoneally. These results indicate that the changes in HGP observed after pretreatment with IND may largely if not completely be due to a non-specific depletion in hepatic glycogen content and that IND does not exert a direct influence on HGP. 相似文献
58.
59.
L. Heinrich 《Biometrical journal. Biometrische Zeitschrift》1995,37(6):726-726
60.
The effect of a variety of structurally diverse antibiotics on C55-isoprenoid-alcohol kinase (EC 2.7.1.66) from Staphylococcus aureus has been examined. Only moenomycin was found to be inhibitory (Ki = 0.2 mM).Moenocinol, The C25 lipid component of moenomycin, did not serve as a substrate of kinase reaction and was less inhibitory than the intact antibiotic.It is concluded that the observed inhibition may be due to the structural similarity between C55-isoprenylmonophosphate and the substituted moenocinol moiety of moenomycin. 相似文献