Inhibitory effect of novel 5-O-acyl juglones on mammalian DNA polymerase activity, cancer cell growth and inflammatory response

We previously found that vitamin K(3) (menadione, 2-methyl-1,4-naphthoquinone) inhibits the activity of human mitochondrial DNA polymerase γ (pol γ). In this study, we focused on juglone (5-hydroxy-1,4-naphthoquinone), which is a 1,4-naphthoquinone derivative, and chemically synthesized novel juglones conjugated with C2:0 to C22:6 fatty acid (5-O-acyl juglones). The chemically modified juglones enhanced mammalian pol inhibition and their cytotoxic and anti-inflammatory activities. The juglone conjugated with oleic acid (C18:1-acyl juglone) showed the strongest inhibition of DNA replicative pol α activity and human colon carcinoma (HCT116) cell growth in 10 synthesized 5-O-acyl juglones. C12:0-Acyl juglone was the strongest inhibitor of DNA repair-related pol λ, as well as the strongest suppression of the production of tumor necrosis factor (TNF)-α production induced by lipopolysaccharide (LPS) in the compounds tested. Moreover, this compound caused the greatest reduction in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced acute inflammation in mouse ears. C12:0- and C18:1-Acyl juglones selectively inhibited the activities of mammalian pol species, but did not influence the activities of other pols and DNA metabolic enzymes tested. These data indicate that the novel 5-O-acyl juglones target anti-cancer and/or anti-inflammatory agents based on mammalian pol inhibition. Moreover, the results suggest that acylation of juglone is an effective chemical modification to improve the anti-cancer and anti-inflammation of vitamin K(3) derivatives, such as juglone.

Inhibitory effects of vitamin K₃ derivatives on DNA polymerase and inflammatory activity

Previously, we reported that vitamin K₃ (menadione, 2-methyl-1,4-naphthoquinone) (compound 2) inhibits the activity of human mitochondrial DNA polymerase γ (pol γ). In this study, we investigated the inhibitory effects (IEs) of vitamin K3 and its derivatives, such as 1,4-naphthoquinone (compound 1) and 1,2-dimethyl-1,4-naphthoquinone (compound 3), on the activity of mammalian pols. Among compounds 1-3 (10 µM for each), compound 1 was the strongest inhibitor of mammalian pols α and λ, which belong to the B and X pol families, respectively, whereas compound 2 was the strongest inhibitor of human pol γ, a family A pol. However, these compounds did not affect the activity of human pol κ, a family Y pol. As we previously found a positive relationship between pol λ inhibition and anti-inflammatory action, we examined whether these vitamin K₃ derivatives are able to inhibit inflammatory responses. Among the three compounds tested, compound 1 caused the greatest reduction in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced acute inflammation in mouse ears. In addition, in a cell culture system using RAW264.7 mouse macrophages, compound 1 displayed the strongest suppression of tumor necrosis factor (TNF)-α production induced by lipopolysaccharide (LPS). In an in vivo mouse model of LPS-evoked acute inflammation, the intraperitoneal injection of compound 1 into mice suppressed TNF-α production in their peritoneal macrophages and serum. In an in vivo colitis mouse model induced using dextran sulfate sodium (DSS), the vitamin K₃ derivatives markedly suppressed DSS-evoked colitis. In conclusion, this study has identified several vitamin K₃ derivatives, such as compound 1, that are promising anti-inflammatory candidates.

Synthesis and biological evaluation of vitamin K derivatives as angiogenesis inhibitor

Ten vitamin K(3) derivatives were synthesized and screened for anti-angiogenic activity. Results indicated that amine derivatives (1a-d) exerted a stronger inhibition effect on angiogenesis compared to alkyl derivatives (2a-d). In addition to being the most potent inhibitor, 1b also suppressed human umbilical vein endothelial cell tube formation and proliferation. These results suggest that vitamin K(3) amine derivatives with shorter alkyl chains, such as 1b, could be useful for developing anti-angiogenic agents.

Multicolour luminescence from InGaN quantum wells grown over GaN nanowire arrays by molecular-beam epitaxy

The luminescence of InGaN single quantum wells grown by molecular-beam epitaxy under fixed conditions over a series of c-axis GaN nanowire arrays with different geometrical parameters was studied. For arrays with variable GaN average wire diameters and fixed wire densities, the InGaN luminescence peak shifted to higher energy with decreasing wire diameter. It is shown that this trend cannot be attributed to lateral quantum confinement or diameter-dependent InGaN strain. For arrays with variable wire densities and fixed average diameters, the InGaN emission appeared as two distinct bands of different colours, the relative intensities of which depended on the wire density. By optimizing both the GaN wire density and InGaN growth conditions, the colours of the two different bands were combined to realize phosphor-free white light-emitting diodes. The mechanisms for the dependence of the InGaN luminescence on the geometrical parameters of the GaN nanowire array are discussed.

Synthesis and structure-activity relationships of dehydroaltenusin derivatives as selective DNA polymerase alpha inhibitors

Herein, we describe the synthesis and structure-activity relationships of dehydroaltenusin derivatives as inhibitors of a mammalian DNA polymerase alpha. We have newly synthesized nine dehydroaltenusin derivatives modified at the side chains or benzoquinone moiety. We also achieved the first synthesis of desmethylaltenusin and desmethyldehydroaltenusin, metabolites of Alternaria sp. or Talaromyces flavus, respectively. Among all synthesized derivatives, demethoxydehydroaltenusin was the most selective inhibitor of DNA polymerase alpha. The o-hydroxy-p-benzoquinone (2-hydroxycyclohexa-2,5-dienone) moiety is essential for the inhibition of DNA polymerases. Substitution at the 5-position of dehydroaltenusin is important for the inhibitory potency. Because dehydroaltenusin is conjugated with N-acetylcysteine methyl ester at the o-hydroxy-p-benzoquinone moiety, one or more cysteine residues of DNA polymerase alpha may act as a target for this compound.

The specific inhibitory effect of demethoxydehydroaltenusin, a derivative of dehydroaltenusin, on mammalian DNA polymerase alpha

In the screening of selective inhibitors of eukaryotic DNA polymerases (pols), dehydroaltenusin from the fungus Acremonium sp. was found to be an inhibitor of pol alpha. The present study succeeded in chemically synthesizing dehydroaltenusin, and the compound strongly inhibited calf pol alpha activity and weakly suppressed rat pol beta activity, with IC50 values of 0.68 and 64 microM, respectively. We purified or synthesized various slightly modified derivatives of dehydroaltenusin, and using these, investigated the relationship between chemical structure and the inhibitory effects. These results suggest that the ketone group at the 5'-position in dehydroaltenusin is essential for pol inhibitory activity, and the group at the 5-position is important for the specificity of pol alpha inhibition. Demethoxydehydroaltenusin was found to be the most specific pol alpha inhibitor among the prepared derivatives, and the IC50 values for pols alpha and beta were 0.24 and 89 microM, respectively. This compound did not influence the activities of other replicative pols such as pols delta and epsilon, and also demonstrated no effect on pol alpha activity from another vertebrate, fish and a plant species. Demethoxydehydroaltenusin also had no influence on the other pols and DNA metabolic enzymes tested. Therefore, demethoxydehydroaltenusin is of interest as a mammalian pol alpha-selective inhibitor as a 'chemical knockout agent' in vitro and in vivo.

Synthesis and Determination of the Absolute Configuration of Chiral Tetracosanaphthalenes

Tetracosanaphthalenes with diethylaminocarbonylmethoxy side chains were constructed by bottom-up synthesis, and their absolute configurations were determined by an exciton chirality method.