Design, Synthesis and Cytotoxicity of Novel Podophyllotoxin Derivatives

Abstract

A series of novel podophyllotoxin derivatives were designed using association strategy and synthesized by coupling either podophyllotoxin (1) or 4b b-amino podophyllotoxin (3) with substituted indol-3-yl-glyoxyl chlorides. Their structures were identified using spectroscopic techniques. These novel derivatives have been evaluated for cytotoxicity in vitro against four human cancer cell lines with comparison to the parent compounds 1, 3 and indibulin (2). Some of the compounds (7a, 7c) showed comparable cytotoxicity to that of podophyllotoxin.Key words podophyllotoxin; indibulin; cytotoxicity; multidrug resistance Chem. Pharm. Bull. 56(6) 831-834 (2008) © 2008 Pharmaceutical Society of Japan * To whom correspondence should be addressed. e-mail: mscheng@syphu.edu.cn Fig. 1 We report herein the synthesis and cytotoxicity of a series of 4a-O-and 4b-N-indol-3-yl-glyoxyl-substituted derivatives of podophyllotoxin. The biological activity of these derivatives was evaluated by in vitro cytotoxicity study.Chemistry The novel podophyllotoxin derivatives 7a-j were prepared according to the general synthetic approach as depicted in Chart 2. The N-substituted indoles 5a-c were readily synthesized by the reaction of indole 4 with an aralkyl chloride in the presence of NaH. Treatment of substituted indoles 5 with oxalyl chloride in diethyl ether gave substituted indol-3-yl-glyoxyl chlorides 6 with a 70-95% yield. Subsequently, 6 was coupled with podophyllotoxin or 4b-amino podophyllotoxin in the presence of triethylamine and 4-(N,N-dimethylamino)-pyridine (DMAP) to generate the products listed in Table 1. As illustrated in Chart 2, 4b-amino podophyllotoxin was prepared from podophyllotoxin according to known procedures. 5,13) Acylation of podophyllotoxin retained the a-configuration of its C-4 carbon atom, which could be deduced from the 1 H-NMR spectral data of 7a-c. In their 1 H-NMR spectra, the J value (8.3 Hz) of the hydrogen atom (d 6.05 or 6.06 ppm) at the C-4 position of 7a-c demonstrates their 4a-configuration. The structures of the resulting compounds were identified by 1 H-NMR and mass spectroscopy. Results and DiscussionThe biological activity of this series of podophyllotoxin derivatives was evaluated by an in vitro cytotoxicity test, which was carried out with a panel of four human cancer cell lines including HeLa (cervix), SKOV3 (ovary), K562 (leukemia) and K562ADR (adriamycin resistant leukemia), using podophyllotoxin (1), indibulin (2), 4b-aminopodophyllotoxin (3) and adriamycin as reference compounds. The screening procedure was based on the standard MTT or SRB method. The IC 50 and GI 50 values are shown in Table 2.As can be seen from the results, most of the derivatives presented substantial in vitro cytotoxic activity, even against the adriamycin resistant leukemia cell line (K562ADR). The potency of some of the compounds (7b, 7c, 7f, 7i, 7j) against K562ADR (the resistant multiple was 31.19) was comparable to those against the common K562 cell line. However, two derivatives (7g, 7h) were unable to inh...

Synthesis of Podophyllotoxin Derivatives as Potential Antitumor Agents

“…N-Substituted 5-formylindoles (2a-h) were synthesized by the literature method [10]. General Procedure for the Synthesis of 5a-q.…”

“…Furthermore, indibulin lacks the neurotoxicity typically associated with other tubulin-binding drugs such as the taxanes and vinca alkaloids, which might be related to its unknown tubulin-binding mode [9]. Both podophyllotoxin and indibulin are potent microtubulin inhibitors, but the indibulinbinding sites of the two compounds are different [10]. This prompted us to design hybrids of indibulin and podophyllotoxin with the aim of discovering novel tubulin inhibitors that can lower podophyllotoxincs toxicity by binding to a novel tubulinbinding domain.…”

“…N-substituted 5-formylindoles 2a-h were coupled with 4E-amino-4c-demethyl-4-desoxypodophyllotoxin 3a or 4E-amino-4-desoxypodophyllotoxin 3b in the presence of acetic acid and anhydrous ethanol and then reduced by NaBH 4 to generate the title compounds 5a-q. Compounds 3a and 3b were prepared from 4c-demethylpodophyllotoxin and podophyllotoxin according to known procedures [10].…”

“…a Reference control (> 98%). 3a: R 1 = H, 3b: R 1 = CH 3 ; 5a: R 1 = R 2 = H; 5b: R 1 = CH 3 , R 2 = H; 5c: R 1 = H, R 2 = 3-Cl-C 6 H 4 CH 2 5d: R 1 = CH 3 , R 2 = 3-Cl-C 6 H 4 CH 2 ; 5e: R 1 = H, R 2 = 2-F-C 6 H 4 CH 2 ; 5f: R 1 = CH 3 , R 2 = 2-F-C 6 H 4 CH 2 5g: R 1 = H, R 2 = C 6 H 5 CH 2 ; 5h: R 1 = CH 3 , R 2 = C 6 H 5 CH 2 ; 5i: R 1 = H, R 2 = p-CH 3 OC 6 H 4 CH 2 5j: R 1 = CH 3 , R 2 = p-CH 3 OC 6 H 4 CH 2 ; 5k: R 1 = H, R 2 = 4-tert-C 4 H 9 -C 6 H 4 CH 2 5l: R 1 = CH 3 , R 2 = 4-tert-C 4 H 9 -C 6 H 4 CH 2 ; 5m: R 1 = H, R 2 = 4-CH 3 -C 6 H 4 CH 2 5n: R 1 = CH 3 , R 2 = 4-CH 3 -C 6 H 4 CH 2 ; 5o: R 1 = H, R 2 = C 2 H 5 ; 5p: R 1 = CH 3 , R 2 = C 2 H 5 5q: R 1 = CH 3 , R 2 = 2-Cl-C 6 H 4 CH 2 a. NaH, DMF, 0qC -r.t., [8][9][10][11][12]b. acetic acid,anhydrous ethanol,r.t.,[3][4][5][6]c.…”

Antitumor activity and pharmacokinetics of podophyllotoxin incorporated into solid lipid nanoparticles

“…However, utility of PPT as an antitumor drug encountered a lot of restrictions because of its toxicity [3] . Recently, efforts are made to develop new derivatives or dosage forms of PPT with optimized curative effect and attenuated toxicity [4,5] . In previous researches, we carried out deep investigations about the antitumor mechanism of PPT and its derivatives [6−8] .…”