Several ring C aromatized analogues of podophyllotoxin were synthesized for testing against human DNA topoisomerase II. The results indicate that aromatization of ring C gave rise to no inhibition of this enzyme at 200 microM. A comparison of the cytotoxicity among these compounds also demonstrates that a free hydroxyl group at C-4 contributes to significant cytotoxicity.
A principal mechanism of action of the clinical antitumor drugs etoposide (1) and teniposide (2) is the inhibition of catalytic activity of type II DNA topoisomerase and concurrent enzyme-mediated production of lethal DNA strand breaks. Substitution of the glycosidic moiety of 1 or 2 by ester and ethers, as well as the esterification and etherification of alpha-peltatin (4) including its glucosidic ethylidene and thenylidene cyclic acetals (25 and 26), has afforded compounds of much less activity than that of 1. The in vitro cytotoxicity (KB) appears to have no correlation with the inhibitory activity of the human DNA topoisomerase II.
Due to the excellent physical and chemical properties of low melting point, high stability, low vapor pressure, and adjustable solubility, the ionic liquid is widely used in the dissolution of cellulose, regeneration and applied research. This thesis selects the ionic liquid to dissolve the wooden ponder in the processed wood residues and observes its dissolution behavior including the dissolution process of the cellulose in the ionic liquid and the cellulose dissolution as well as its regeneration mechanism. It turns out that the chemical structure of successfully prepared gel-type wood composite material does not changes and its microstructure retains a complete timber microscopic structure. For the fiber bundle formed after the celluloses dissolution, one part functions as the support skeleton, another forms a closed three-dimensional crosslinked network, which possesses stable chemical and physical properties. The gel-type wood composites owns suitable visual characteristics, which can render the "natural", "comfortable", "simple and elegant", and "crisp" visual psychological impression.
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