Antioxidative and antitumor activity of derivatives of 4-beta-amino-4'-demethylepipodophyllotoxin and their structure-activity relationship.
The purpose of this study was to investigate antioxidative and antitumor activity of derivatives of 4-beta-amino-4'-demethylepipodophyllotoxin (DmePod) and to analyze their structure-activity relationship. Homogenates of liver, heart and kidney of rats were used to measure malondialdehyde (MDA) generation spontaneously formed or induced by a hydroxyl free radical generation system (Fe2+-ascorbic acid) using thiobarbituric acid (TBA) assay. H2O2-induced red blood cells (RBC) hemolysis was determined spectrophotometrically. Superoxide anion (O2-*) from zymosan-stimulated neutrophils of rats was evaluated by nitroblue tetrazolium (NBT) reduction assay. Microculture tetrazolium (MTT) assay was used to determine the antitumor effects on K562 and K562/DOX cells. The results showed that all the tested compounds strongly inhibited MDA formation from tissue homogenates in a concentration-dependent manner following the rank GP7OH > GP7 > VP16 and GP7H > DmePod > Pod. The potency of antihemolysis for DmePod, GP7, GP7OH, GP7H and VP16 was similar among them according to their IC50 values by 13.6, 8.6, 11.7, 10.3, and 9.47 micromol x L(-1), respectively, whereas the potency for Pod was the weakest (IC50 > 320 micromol x L(-1)). GP7, GP7OH and VP16 (160-320 [micromol x L(-1)) significantly inhibited O2-* formation following the potency rank VP16 > GP7 > GP7OH. However, 320 micromol x L(-1) of DmePod, Pod or GP7H had no effect on O2-* formation. Meanwhile, all the tested compounds strongly inhibited K562 and K562/DOX cell proliferation for 96 h in a concentration-dependent manner. The resistance magnitude of GP7, GP7OH, VP16, and DmePod was 2.05, 2.21, 14.29, and 3.26, respectively, while antitumor activity of Pod and GP7H on K562/DOX cells was the weakest in all compounds. Taken together, the introduction of nitroxyl radical moieties into DmePod greatly enhances antioxidative and antitumor activity, and reverses drug resistance. Both NO* and NOH groups are essential active moieties.
Zhang
Xiao-Yu
XY
College of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, PR China. zhangxiaoyuly@yahoo.com.cn
Li
Wen-Guang
WG
Wu
Yong-Jie
YJ
Tian
Xuan
X
D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000494:pharmacology*; D000975:Antioxidants / Q000138:chemical synthesis* / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects; D004912:Erythrocytes / Q000187:drug effects; D005260:Female; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007202:Indicators and Reagents; D020014:K562 Cells; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects; D011034:Podophyllotoxin / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D051381:Rats; D013329:Structure-Activity Relationship; D013481:Superoxides / Q000378:metabolism; D013778:Tetrazolium Salts; D013844:Thiazoles
D000970:Antineoplastic Agents; D000975:Antioxidants; D007202:Indicators and Reagents; D013778:Tetrazolium Salts; D013844:Thiazoles; D013481:Superoxides; D008315:Malondialdehyde; D006861:Hydrogen Peroxide; C022616:thiazolyl blue; D011034:Podophyllotoxin; C072088:4'-demethylepipodophyllotoxin