Search results for "Cyclic compound"
showing 10 items of 819 documents
Morphogenesis in Root Tip Meristem Cultures of Digitalis obscura L.
1987
Summary The morphogenic capacity of Digitalis obscura L. root tip meristems cultured in vitro has been studied, noting hormonal factors inducing differentiation and development of shoots as well as those promoting somatic embryogenesis. Caulogenesis was obtained with different auxin/cytokinin combinations but a high rate of shoot regeneration was induced by 0.1 or 0.5 ppm IAA and 1.0 ppm BA. Different stages of somatic embryo development were observed in media supplemented with auxins or high auxin/cytokinin ratios, although no complete plant regeneration was achieved. This is the first report known of shoot regeneration from root tips of Digitalis obscura L.
Plant regeneration from cultured leaves of Lavandula latifolia Medicus: Influence of growth regulators and illumination conditions
1989
Leaves were obtained from 4-week-old seedlings of Lavandula latifolia Medicus grown in vitro. Leaf explants were then cultured on MS medium supplemented with different concentrations and combinations of the auxins IAA or NAA with the cytokinin BA and maintained under three illumination conditions, 16h photoperiod, darkness or darkness followed by a photoperiod, to assess morphogenic responses. Irrespective of illumination conditions, bud regeneration was achieved only in media containing BA or BA/auxin combinations, with the best results being obtained in the presence of BA and 0.06 or 0.6 μM IAA or NAA. A photoperiod of 16h appeared to yield the best response in terms of bud regeneration p…
Regioselective Annulation of Alicyclic−Aromatic Dienes with 3-Halo-3-cyclobutene-1,2-diones. Synthesis of Annulated α-Halobenzocyclobutenones1
1998
4-(1-Cycloalken-1-yl)-1,2-dialkoxybenzenes 8, 10, and 11 and 5-(1-cycloalken-1-yl)-1,3-benzodioxoles 12−15 react with the semisquaric halides 5a and 5b in a dehydrative annulation process to give the annulated α-halobenzocyclobutenones 9a,b and 16a,b−21a,b in poor to good yields (20−76%). The reaction failed with alicyclic−aromatic dienes having no or only one alkoxy group in the benzene ring. The dehydrative annulation process could be extended to 4-(3,4-dimethoxyphenyl)-1,2-dihydronaphthalene (24), affording the highly annulated α-chlorobenzocyclobutenone 25 in 50% yield. In the case of 5-(1-cyclobuten-1-yl)-1,3-benzodioxole (22), reaction with the semisquaric halides 5a,b yielded the dic…
Novel Porphyrin-Cholic Acid Conjugates as Receptors for Biologically Important Anions
2005
A series of novel receptors showing high binding affinity in aqueous media for biologically important anions are reported. These naturally chromophoric porphyrin-based receptors contain cholic acids connected via quaternary alkyl ammonium amido linkages.
Dihydrodiol Dehydrogenase: An Important Enzyme in Dihydrodiol-Epoxide Pathway — Mediated Benzo(A)Pyrene Mutagenicity
1978
Benzo(a)pyrene is metabolized to two major groups of mutagenically reactive metabolites: Monofunctional epoxides and dihydrodiol-epoxides. Various monooxygenase forms catalyze the various pathways at very different rates. In metabolic situations where the contribution by dihydrodiol-epoxides is small, epoxide hydratase represents a very efficient protective system. However, in situations where the mutagenic effect is predominately due to dihydrodiol-epoxide, the effect of epoxide hydratase is complicated and weak. We have now obtained evidence that a dihydrodiol dehydrogenase represents an efficient protective system in the latter situation. The enyzme was purified to homogeneity and the pu…
Dihydrodiol Dehydrogenase: Substrate Specificity, Inducibility and Tissue Distribution
1982
The present study shows that: Dihydrodiol dehydrogenase activity is present in the 100,000 g supernatant fraction of extrahepatic tissues. Dihydrodiol dehydrogenase is able to oxidize the hydroxy group and to reduce the keto group of a number of xenobiotics including quinones derived from polycyclic aromatic hydrocarbons. Dihydrodiol dehydrogenase was not inducible by various substances including hormones, polycyclic aromatic hydrocarbons, substrates of the enzyme and potent inducers of monooxygenases, epoxide hydrolase and glutathione S-transferases. Only in the case of thyroxine was a weak induction with a high dose of the hormone observed.
Individual Differences in DNA Repair Capacities in Man
1987
After metabolic activation of benzo[a]pyrene to the 7,8-dihydrodiol- 9,10-epoxide, this ultimate carcinogen preferentially binds to the exocyclic amino group of guanine. In order to investigate possible interindividual differenes in the capacity of repair of the DNA adducts formed from benzo[a]- pyrene 7,8-dihydrodiol 9,10-epoxide, their persistence in freshly isolated lymphocytes of several donors was studied. The results show a surprisingly large interindividual variation in DNA adduct formation and their persistence in freshly isolated lymphocytes. This range included several individuals with an apparent complete lack of repair capability for these adducts. Compared with controls, smoker…
Neue Diels-Alder-Reaktionen von 1-Methylpyrano[3,4-b]indol-3(9H)-on mit cyclischen CC-Dienophilen: ein einfacher Zugang zu [b]anellierten Carbazol-De…
1988
1-Methylpyrano[3,4-b]indol-3(9H)-on (1) reagiert als synthetisches Aquivalent von Indolo-2,3-chinodimethan mit Arin, p-Benzochinon und p-Naphthochinon zu neuen [b]anellierten Carbazol-Derivaten. Durch das Reaktionsmedium bedingt lassen sich bei der Cycloaddition von 1 mit Arin zugleich auch mononitrierte Carbazole isolieren. New Diels-Alder Reactions of 1-Methylpyrano[3,4-b]indol-3(9H)-one with Cyclic CC-Dienophiles: A Simple Way to [b]Annulated Carbazole Derivatives. 1-Methylpyrano[3,4-b]indol-3-(9H)-one (1) reacts as synthetic equivalent of indolo-2,3-quinodimethane with benzyne, p-benzoquinone, and p-naphthoquinone to give new [b]annulated carbazole derivatives. In the Diels-Alder reacti…
Separation of aromatic aminophosphonic acid enantiomers by capillary electrophoresis with the application of cyclodextrins
2002
The detailed studies concerning capillary electrophoresis separation of aminophosphonic acid enantiomers with various commercially available cyclodextrins are presented. The obtained results show that the separation of these stereoisomers is dependent on pH of background electrolyte, concentration of cyclodextrin as well as on the type of applied chiral selector. The separation mechanism is based on the co-operative effect of hydrogen bond type interactions enhanced by hydrophobic forces and sterical constrains between aminophosphonate and cyclodextrin. With application of elaborated method, enantiomeric baseline or partial separation of 18 alpha-aminophosphonic acids was achieved. This sep…
Alkaloids from Rauwolfia serpentina cell cultures treated with ajmaline
1993
Abstract A group of new alkaloids, the raumaclines, and some related alkaloids were isolated from Rauwolfia serpentina cell suspensions fed with high levels of ajmaline; their structures were determined and syntheses developed providing an essential prerequisite to the further study of their biosynthesis at the enzymatic level.