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Alkyl-substituted cyclobutanetetracarboxylic dianhydrides (CBDAs) were synthesized by photo-dimerization of alkylsubstituted maleic anhydrides to obtain novel colorless polyimides (PIs). Dimethyl-substituted CBDA (DM-CBDA) showed much higher polymerizability with various diamines than conventional cycloaliphatic tetracarboxylic dianhydrides and led to high molecular weights of PI precursors. Polyaddition of non-substituted CBDA and trans-1,4-cyclohexanediamine (t-CHDA) was completely inhibited by salt formation in the initial reaction stage. The use of DM-CBDA allowed the formation of a homogeneous/viscous PI precursor solution by overcoming the salt formation problem. The prominent substituent effect probably reflects how the methyl substituents of DM-CBDA contributed to increasing the salt solubility. Some of the thermally imidized DM-CBDA-based systems simultaneously possessed non-coloration, low coefficient of thermal expansion (CTE), very high T g exceeding 300 • C and very low dielectric constant. Copolymerization was very effective for improving the solubility of DM-CBDA-based PIs. The copolyimide cast films prepared via chemical imidization displayed a further decreased CTE without sacrificing other target properties, suggesting that the present materials can be useful as plastic substrates in display devices. The mechanism of self-chain orientation behavior during solution casting is also discussed. A potential application of the copolyimide systems as optical compensation film materials in liquid crystal displays is proposed.

The mitochondrial production of reactive oxygen species has been implicated in the anticancer activity of furanonaphthoquinone. However, the mechanism of the activation remains elusive. In the current study, we found that treatment of HeLa cells with 2-methyl-5(or -8)-hydroxy-furanonaphthoquinone (FNQ13) induces mitochondrial swelling, followed by apoptosis. This toxic effect of FNQ13 was reduced by the radical scavengers alpha-tocopherol and trolox. Cytochemical experiments in isolated mitochondria showed that a combination of FNQ13 and NADH induces the production of H(2)O(2) at the exterior mitochondrial membrane surface. This production of H(2)O(2) was reduced by an antibody to the voltage-dependent anion channel (VDAC). Overexpression of the VDAC by transfection with vdac1 cDNA increased the production of H(2)O(2) by HeLa cells, whereas transfection with a small interfering RNA to VDAC reduced FNQ13-induced H(2)O(2) production and cell death due to an almost complete knockdown of VDAC expression. We also found significant correlations between the expression of VDAC and the induction of H(2)O(2) production and cell death by FNQ13 in 11 human cancer cell lines. These results indicate that the anticancer activity of furanonaphthoquinones depends on the production of reactive oxygen species by mitochondrial permeability transition pores including the VDAC.

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Quinones are important naturally occurring pigments widely distributed in nature and are well known to demonstrate various physiological activities as antimicrobial and anticancer compounds. This review will focus on the preparation, therapeutic application, and administration of several benzoquinones, naphthoquinones, and anthraquinones having anti-infective, e.g. antiviral and antibacterial activities, in recent patents.