PubMed · 14033233
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S KIYONO, J MATSUMOTO. 1963. Reflex convulsion.. https://pubmed.ncbi.nlm.nih.gov/14033233/
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Oxo-titanium phthalocyanine (TiOPc) derivatives of catechin and hematoxylin (natural ortho-diol type chiral compounds) have been prepared and characterized by spectral and chromatographic techniques. It is demonstrated that the TiOPc unit is an excellent template for chiral recognition through its isolated Q-transitions. The formation of a helical dimeric complex with hematoxylin induces strong CD-activity in the Q-band region. Ab initio geometry optimizations were combined with a Kuhn-Kirkwood coupled-oscillator mechanism to obtain the absolute configuration of hematoxylin. In addition, it is shown that the described chiroptical recognition method is sensitive to slight conformational changes.
The nuclease activities of a series of hydroxystilbeneoids have been studied so as to establish a structure-activity correlation and deduce the mechanistic pathway of the process. Although the test compounds could nick plasmid DNA, only three of these including resveratrol produced double strand breaks in DNA. Amongst these new stilbenes, compound 2e containing a partially methylated catechol and a C-4 hydroxy moieties was equally potent as resveratrol. The activities of the unprotected catechol-derivatives were less than those of the resorcinol-derivatives, which were, however, compensated by partial methylation of the former. The presence of Cu(2+) and O(2) and the participation of a Cu(+)-oxo intermediate were obligatory in the process which did not require addition of any external reducing agent. Overall, the differential nuclease activities of the compounds could be explained primarily with their superoxide anion generation abilities, and to a lesser extent with their DNA binding and Cu(2+) reducing capacities. The amount of superoxide anion produced by the compounds depended strongly on their Cu(+)-complexation abilities, which again, was decided by the pattern and nature of the oxygenated substituents in the aromatic rings.
4-Nitrocatechol (4NC) is a known inhibitor of lipoxygenase. This work presents the X-ray structure of soybean lipoxygenase-3 in complex with 4NC refined at 2.15 A resolution. The X-ray analysis shows 4NC near iron with partial occupancy, blocking access to Fe but not covalently bound to it. The two hydroxyl groups interact with the C-terminus (4-OH) and His523 ND1 (3-OH). The residues surrounding the iron cofactor, His518*, His523, His709, Ile857* COO(-) and water, form a trigonal bipyramid with the residues marked with asterisks in the axial positions. The water bound to iron and the presence of the inhibitor seem to be responsible for the rearrangements and changes in the geometry of the ligand distribution and confirm the displacement of His518 from iron coordination. A description of the catechol binding contributes to the understanding of lipoxygenase inhibition and the participation of its co-oxidative activity in the utilization of natural flavonoids.