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161.
The investigation of three further species belonging to the subtribe Gochnatiinae, tribe Mutisieae, afforded in addition to known compounds two new eudesmane derivatives and two new germacranolides, closely related to albicolide and salonitenolide. The structures are elucidated by spectroscopic methods and some chemical transformations. The chemotaxonomic aspects are discussed briefly. 相似文献
162.
The investigation of seven Bolivian Senecio species afforded in addition to known compounds five new furanoeremophilanes, two C10-amides, a new isoeugenol ester and the isomer of pterophorin. The structures are elucidated mainly by spectroscopic methods. While most of the new compounds are closely related to those isolated before from Senecio species, four of them are unusual. Another is a new type of a furanoeremophilane; its biogenesis however, can be explained easily from known types. 相似文献
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Andrea Polle Lars O. Baumbusch Christa Oschinski Monika Eiblmeier Vivian Kuhlenkamp Birgit Vollrath Florian Scholz Heinz Rennenberg 《Oecologia》1999,121(2):149-156
Clones of Norway spruce (Picea abies L.) were grown for several years on an altitudinal gradient (1750 m, 1150 m and 800 m above sea level) to study the effects
of environmental × genetic interactions on growth and foliar metabolites (protein, pigments, antioxidants). Clones at the
tree line showed 4.3-fold lower growth rates and contained 60% less chlorophyll (per gram of dry matter) than those at valley
level. The extent of growth reduction was clone-dependent. The mortality of the clones was low and not altitude-dependent.
At valley level, but not at high altitude, needles of mature spruce trees showed lower pigment and protein concentrations
than clones. In general, antioxidative systems in needles of the mature trees and young clones did not increase with increasing
altitude. Needles of all trees at high altitude showed higher concentrations of dehydroascorbate than at lower altitudes,
indicating higher oxidative stress. In one clone, previously identified as sensitive to acute ozone doses, this increase was
significantly higher and the growth reduction was stronger than in the other genotypes. This clone also displayed a significant
reduction in glutathione reductase activity at high altitude. These results suggest that induction of antioxidative systems
is apparently not a general prerequisite to cope with altitude in clones whose mother plants originated from higher altitudes
(about 650–1100 m above sea level, Hercycnic-Carpathian distribution area), but that the genetic constitution for maintenance
of high antioxidative protection is important for stress compensation at the tree line.
Received: 13 October 1998 / Accepted: 22 June 1999 相似文献
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Sabrina Krautbauer Kristina Eisinger Yvonne Hader Markus Neumeier Christa Buechler 《Molecular and cellular biochemistry》2014,393(1-2):69-76
Adipogenesis is associated with the upregulation of the antioxidative enzyme manganese superoxide dismutase (MnSOD) suggesting a vital function of this enzyme in adipocyte maturation. In the current work, MnSOD was knocked-down with small-interference RNA in preadipocytes to study its role in adipocyte differentiation. In mature adipocytes differentiated from these cells, proteins characteristic for mature adipocytes, which are strongly induced in late adipogenesis like adiponectin and fatty acid-binding protein 4, are markedly reduced. Triglycerides begin to accumulate after about 6 days of the induction of adipogenesis, and are strongly diminished in cells with low MnSOD. Proteins upregulated early during differentiation, like fatty acid synthase and cytochrome C oxidase-4, are not altered. Cell viability, insulin-mediated phosphorylation of Akt, antioxidative capacity (AOC), superoxide levels, and heme oxygenase 1 with the latter being induced upon oxidative stress are not affected. L-Buthionine-(S,R)-sulfoximine (BSO) depletes glutathione and modestly lowers AOC of mature adipocytes. Addition of BSO to 3T3-L1 cells 3 days after the initiation of differentiation impairs triglyceride accumulation and expression of proteins induced in late adipogenesis. Of note, proteins that increased early during adipogenesis are also diminished, suggesting that BSO causes de-differentiation of these cells. Preadipocyte proliferation is not considerably affected by low MnSOD and BSO. These data suggest that glutathione and MnSOD are essential for adipogenesis. 相似文献
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169.
Magnolol (4-allyl-2-(5-allyl-2-hydroxyphenyl)phenol), the main bioactive constituent of the medicinal plant Magnolia officinalis, and its main metabolite tetrahydromagnolol were recently found to activate cannabinoid (CB) receptors. We now investigated the structure-activity relationships of (tetrahydro)magnolol analogs with variations of the alkyl chains and the phenolic groups and could considerably improve potency. Among the most potent compounds were the dual CB1/CB2 full agonist 2-(2-methoxy-5-propyl-phenyl)-4-hexylphenol (61a, K
i CB1∶0.00957 µM; K
i CB2∶0.0238 µM), and the CB2-selective partial agonist 2-(2-hydroxy-5-propylphenyl)-4-pentylphenol (60, K
i CB1∶0.362 µM; K
i CB2∶0.0371 µM), which showed high selectivity versus GPR18 and GPR55. Compound 61b, an isomer of 61a, was the most potent GPR55 antagonist with an IC50 value of 3.25 µM but was non-selective. The relatively simple structures, which possess no stereocenters, are easily accessible in a four- to five-step synthetic procedure from common starting materials. The central reaction step is the well-elaborated Suzuki-Miyaura cross-coupling reaction, which is suitable for a combinatorial chemistry approach. The scaffold is versatile and may be fine-tuned to obtain a broad range of receptor affinities, selectivities and efficacies. 相似文献
170.
Phylogenetic distribution of catalase-peroxidases: are there patches of order in chaos? 总被引:1,自引:0,他引:1
Hydrogen peroxide features in many biological oxidative processes and must be continuously degraded enzymatically either via a catalatic or a peroxidatic mechanism. For this purpose ancestral bacteria evolved a battery of different heme and non-heme enzymes, among which heme-containing catalase-peroxidases (CP) are one of the most widespread representatives. They are unique since they can follow both H(2)O(2)-degrading mechanisms, the catalase activity being clearly dominant. With the fast increasing amount of genomic data available, we were able to perform an extensive search for CP and found almost 300 sequences covering a large range of microorganisms. Most of them were encoded by bacterial genomes, but we could also find some in eukaryotic organisms other than fungi, which has never been shown until now. Our screen also reveals that approximately 60% of the bacteria do not possess CP genes. Chaotic distribution among species and incongruous phylogenetic reconstruction indicated existence of numerous lateral gene transfers in addition to duplication events and regular speciation. The results obtained show an impressively complex gene transmission pattern, and give some new insights about the role of CP and the origin of life on earth. Finally, we propose for the first time bacterial candidates that may have participated in the transfer of CP from bacteria to eukaryotes. 相似文献