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101.
Labeled mevalonate is incorporated into terpenes and hop bitter compounds by Humulus lupulus. The role of mevalonate as a precursor for the prenyl (3-methyl-but-2-enyl) side chain of the hop bitter compounds is discussed. 相似文献
102.
Morris Levy 《Biochemical Systematics and Ecology》1976,4(4):249-254
The effects of colchicine induced autotetraploidy on non-anthocyanin flavonoid expression were determine for 15 cultivars of Phlox drummondii and for the naturally occuring P. drummondii ssp. mcallisteri. Collectively, the taxa express a total of nine glycoflavonoid derivatives (C, O-diglycosides or di-C-glycosides) of either apigenin or luteolin. The autotetraploids of 14 cultivars and those of the natural subspecies exhibit altered glycoflavone profiles relative to their respective diploid sources. The qualitative alternations in the cultivars may be grouped into three phenotypic categories: (1) the expression of novel glycoflavones, (2) the absence of diploid glycoflavones, and (3) the deregulation of tissue-specific glycoflavone production. Alterations in mcallisteri autotetraploids include only the latter two categories. Each of the novel compounds is otherwise expressed among other diploid cultivars or in other wild P. drummondii subspecies. Quantitatively, the phenolic content of most autotetraploid flowers is significantly greater than in respective diploid flowers. However, on a dry weight basis, phenolic titre in comparable 4n and 2n floral or leaf tissues is not significantly different. Floral tissues express from 5 to 10 times the phenolic titre of leaves. The results are discussed in terms of the possible origins of novel flavonoids in natural polyploid Phlox species. 相似文献
103.
In axenic Chlorella pyrenoidosa Chick cultures, extracellular release was linear with time, but plateau-type curves were obtained in cultures with added bacteria. Initial rates of excretion were identical in both, systems. Kinetics of extracellular release in axenic Anabaena flos-aquae (Lyng.) Bréb. cultures were more complex than in Chlorella but the initial excretion rates were identical in axenic and mixed algal-bacterial cultures. In lakewater, extracellular release kinetics resemble the pattern in mixed Chlorella-bacteria cultures. An explanation is an initial lag in bacterial utilization of algal extracellular products. As a result, both in situ and in the laboratory, consecutive short, experiments give higher excretion rates than single long incubations. It is suggested that the former are close to total or gross extracellular release rates whereas the latter give net values, detecting only substances not, removed by heterotrophs. 相似文献
104.
140 Organophosphorus compounds (OP's) have been tested for mutagenic activity in bacteria, principally by using two specially constructed sets of tester strains of the bacteria Salmonella typhimurium and Escherichia coli. It was found that 20% gave positive mutagenic responses and that this group of chemicals produce base substitutions rather than frame-shift mutations. In most cases the DNA repair genes exrA+ and recA+ were for mutagenic activity.Seven compounds were further tested in Drosophila melanogaster for the ability to induce recessive lethal mutations. In some of these cases the doses administered to the flies had to be very low due to the highly toxic nature of the compounds. To overcome this problem, the accumulation of recessive lethal mutations was measured in populations which were continually exposed to the compounds over a period of some 18 months. During this time the populations developed increased resistance to the compound and so the dose administered could gradually be increased. Six of the compounds were mutagenic.Of the compounds tested in both systems, those showing mutagenic activity in bacteria were also mutaganic in Drosophila, those mutagenic in bacteria were not mutagenic in Drosophila. 相似文献
105.
106.
K. Sigler D. Matoulková M. Dienstbier P. Gabriel 《Applied microbiology and biotechnology》2009,82(6):1027-1035
The net effect of increased wort osmolarity on fermentation time, bottom yeast vitality and sedimentation, beer flavor compounds,
and haze was determined in fermentations with 12° all-malt wort supplemented with sorbitol to reach osmolarity equal to 16°
and 20°. Three pitchings were performed in 12°/12°/12°, 16°/16°/12°, and 20°/20°/12° worts. Fermentations in 16° and 20° worts
decreased yeast vitality measured as acidification power (AP) by a maximum of 10%, lowered yeast proliferation, and increased
fermentation time. Repitching aggravated these effects. The 3rd “back to normal” pitching into 12° wort restored the yeast
AP and reproductive abilities while the extended fermentation time remained. Yeast sedimentation in 16° and 20° worts was
delayed but increased about two times at fermentation end relative to that in 12° wort. Third “back-to-normal” pitching abolished
the delay in sedimentation and reduced its extent, which became nearly equal in all variants. Beer brewed at increased osmolarity
was characterized by increased levels of diacetyl and pentanedione and lower levels of dimethylsulfide and acetaldehyde. Esters
and higher alcohols displayed small variations irrespective of wort osmolarity or repitching. Increased wort osmolarity had
no appreciable effect on the haze of green beer and accelerated beer clarification during maturation. In all variants, chill
haze increased with repitching. 相似文献
107.
Saeid Kalantari-Dehaghi Bahman Ebrahimi-Hosseinzadeh Zahra-Beagom Mokhtari-Hosseini Fahimeh Nojoki Javad Hamedi 《Preparative biochemistry & biotechnology》2013,43(3):286-297
AbstractCo-v-culture (co-cultivations of physically separated microbes that only interact through the air) systems were designed to investigate the effects of microbial volatile organic compounds (mVOCs) from about 20 different microbes, on a medicinal fungus, Ganoderma lucidum. For more accuracy in co-cultivations, a novel synchronized cultivation approach was tested for culturing G. lucidum. The hyphal growth of G. lucidum and the content of its ganoderic acids (GAs) were measured. In almost all of the co-v-cultures, there was an inhibiting effect on hyphal growth and a promoting effect on GAs contents. In inducing GAs production, Bacillus cereus PTCC 1247 and Pseudomonas aeruginosa UTMC 1404 were the most effective ones, as, compared to control cultures, GAs content increased 2.8 fold. Comparing different co-v-cultivations demonstrated that the concentrations of mVOCs, oxygen, and carbon dioxide were the main players in co-v-cultures. No correlation was found between hyphal growth and GAs production. Strains of the same species imposed totally different effects on hyphal growth or GAs production. This study has investigated the effects of mVOCs on G. lucidum for the first time. Moreover, it suggests that co-v-cultivation may be a promising biotechnological approach to improve the production in G. lucidum. 相似文献
108.
To explore new scaffolds for the treat of Alzheimer’s disease appears to be an inspiring goal. In this context, a series of varyingly substituted flavonols and 4-thioflavonols have been designed and synthesized efficiently. All the newly synthesized compounds were characterized unambiguously by common spectroscopic techniques (IR, 1H-, 13C NMR) and mass spectrometry (EI-MS). All the derivatives (1–24) were evaluated in vitro for their inhibitory potential against cholinesterase enzymes. The results exhibited that these derivatives were potent selective inhibitors of acetylcholinesterase (AChE), except the compound 11 which was selective inhibitor of butyrylcholinesterase (BChE), with varying degree of IC50 values. Remarkably, the compounds 20 and 23 have been found the most potent almost dual inhibitors of AChE and BChE amongst the series with IC50 values even less than the standard drug. The experimental results in silico were further validated by molecular docking studies in order to find their binding modes with the active pockets of AChE and BChE enzymes. 相似文献
109.
110.
《Biocatalysis and Biotransformation》2013,31(1):102-110
The chronic wound environment is characterized by high concentrations of reactive oxygen species (ROS) and elevated levels of myeloperoxidase (MPO) and collagenases, together impairing the healing process. Therefore, the management of chronic wounds at a molecular level requires the synergistic use of antioxidants, MPO and collagenase inhibitors to simultaneously target multiple factors from wound pathogenesis. In this study, a polyphenolic extract from Hamamelis virginiana plant, rich in condensed and hydrolysable oligomeric tannins, was evaluated as an inhibitor of MPO and collagenase. In addition to efficient scavengers of radical and non-radical reactive species, H. virginiana polyphenols were found to act as substrates in the MPO peroxidase cycle, preventing the accumulation of ROS in the chronic wound site. Furthermore, it was also found that the plant exerts an irreversible inhibitory effect on collagenase activity (IC50 = 75 ± 10 μg/mL). 相似文献