Topoisomerase I , inhibition

Topoisomerases are fundamental enzymes that ensure DNA replication, transcription, or recombination [66]. Both type I and type II topoisomerases act by changing 

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Ganguly A, Das B, Roy A, Sen N, Dasgupta SB, Mukhopadhayay S, Majumder HK. (2007) Betulinic acid, a catalytic inhibitor of topoisomerase I, inhibits reactive oxygen species-mediated apoptotic topoisomerase I-DNA cleavable complex formation in prostate cancer cells but does not affect the process of cell death. Cancer Res 67 11848-11858. 

Von Pawel J. Topotecan (Hycamtin) potent cytostatic action by selective topoisomerase I inhibition. Onkologie 1997 20 380-6. 

As noted earlier, the bioassay is capable of detecting topoisomerase I inhibition activity as well as topoisomerase II inhibition activity. It is thus interesting that we found no extracts that showed the topoisomerase I pattern of activity, indicating the scarcity of natural products with this activity and enhancing the uniqueness of camptothecin (12) and its derivatives. Of course, by the same token, the discovery of a new topoisomerase I inhibitor would be a noteworthy event. 

Mechanisms of Topoisomerase I Inhibition by Anticancer Drugs Yves Pommier, Akihiko Tanizawa, and Kurt W. Kohn... 

Figure 3 shows the alkaloids with the pyrrolo[4,3,2-de]pyrrolo[2,3-/t]quinoline skeleton, i.e., wakayin and tsitsikammamines. Wakayin was isolated from a Fijian ascidian and is the first pyrroloiminoquinone alkaloid not isolated from a marine sponge [19]. Tsitsikammamines A and B were isolated from a South African latrunculid sponge Latrunculiidae in 1996 [20]. They are reported to exhibit a cytotoxicity and topoisomerase I inhibition. Furthermore, reinvestigation of the extracts of the same sponge led to isolation of minor pyrroloiminoquinone... 

R 410 L. F. Gladden, Recent Advances in MRI Studies of Chemical Reactors Ultrafast Imaging of Multiphase Flows , Top. Catal, 2003,24,19 R 411 W. H. Gmeiner, S. Yu, R. T. Pon, P. Pourquier and Y. Pommier, Structural Basis for Topoisomerase I Inhibition by Nucleoside Analogs , Nuc-leos. Nucleot. Nucl., 2003,22, 653... 

The cytotoxicities and topoisomerase I inhibition of these compounds (Figure 3) were tested in cancer cells in comparison with dieir parent compounds. As shown in Table I, those compounds widi glucose moiety (1, 2... 

Shobani AM, Ebrahimi SA, Mahmoudian M (2002) An in vitro evaluation of human DNA topoisomerase I inhibition by Peganum harmala L. seeds extract and its beta-carboline alkaloids. J Pharm Pharmaceut Sci 5 19-23... 

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