Synthesis and Cytotoxicity Evaluation of Novel Podophyllotoxin Derivatives

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

Recent Advances in the Chemistry and Biology of Podophyllotoxins

Podophyllotoxin and its related aryltetralin cyclolignans belong to a family of important products that exhibit various biological properties (e.g., cytotoxic, insecticidal, antifungal, antiviral, anti-inflammatory, neurotoxic, immunosuppressive, antirheumatic, antioxidative, antispasmogenic, and hypolipidemic activities). This Review provides a survey of podophyllotoxin and its analogues isolated from plants. In particular, recent developments in the elegant total chemical synthesis, structural modifications, biosynthesis, and biotransformation of podophyllotoxin and its analogues are summarized. Moreover, a deoxypodophyllotoxin-based chemosensor for selective detection of mercury ion is described. In addition to the most active podophyllotoxin derivatives in each series against human cancer cell lines and insect pests listed in the tables, the structure-activity relationships of podophyllotoxin derivatives as cytotoxic and insecticidal agents are also outlined. Future prospects and further developments in this area are covered at the end of the Review. We believe that this Review will provide necessary information for synthetic, medicinal, and pesticidal chemistry researchers who are interested in the chemistry and biology of podophyllotoxins.

Antineoplastic Agents. 585. Isolation of Bridelia ferruginea Anticancer Podophyllotoxins and Synthesis of 4-Aza-podophyllotoxin Structural Modifications

Cytotoxic constituents of the terrestrial plant Bridelia ferruginea were isolated using bioactivity-guided fractionation, which revealed the presence of the previously known deoxypodophyllotoxin (1), isopicrodeoxypodophyllotoxin (2), β-peltatin (3), β-peltatin-5-O-β-D-glucopyranoside (3a), and the indole neoechinulin (4). As an extension of previous podophyllotoxin research, SAR studies were undertaken focused on 4-aza-podophyllotoxin structural modifications. A number of such derivatives were synthesized following modifications to the A and E rings. Such structural modifications with alkyl and 4-fluorobenzyl substituents at the 4-aza position provided the most potent cancer cell growth inhibitory activity (GI50 0.1 to <0.03 μg/mL) against a panel of six human cancer cell lines and one murine cancer cell line. Several compounds corresponding to 4'-demethylated modifications were also synthesized and found to be significantly less potent.

Recent progress on C-4-modified podophyllotoxin analogs as potent antitumor agents

Podophyllotoxin (PPT), as well as its congeners and derivatives, exhibits pronounced biological activities, especially antineoplastic effects. Its strong inhibitory effect on tumor cell growth led to the development of three of the most highly prescribed anticancer drugs in the world, etoposide, teniposide, and the water-soluble prodrug etoposide phosphate. Their clinical success as well as intriguing mechanism of action stimulated great interest in further modification of PPT for better antitumor activity. The C-4 position has been a major target for structural derivatization aimed at either producing more potent compounds or overcoming drug resistance. Accordingly, numerous PPT derivatives have been prepared via hemisynthesis and important structure-activity relationship (SAR) correlations have been identified. Several resulting compounds, including GL-331, TOP-53, and NK611, reached clinical trials. Some excellent reviews on the distribution, sources, applications, synthesis, and SAR of PPT have been published. This review focuses on a second generation of new etoposide-related drugs and provides detailed coverage of the current status and recent development of C-4-modified PPT analogs as anticancer clinical trial candidates.

Design, synthesis, and antitumor activity of novel podophyllotoxin derivatives as potent anticancer agents

In order to find novel synthetic compounds with superior antitumor activity and overcome multidrug resistance, a series of novel 4β-N-substituted podophyllotoxin derivatives were synthesized under mild conditions with satisfactory yield. Nine novel podophyllotoxin derivatives were synthesized by linking 4β-amino-podophyllotoxin with aldehydes via the formation of a Schiff's base, and imines were reducted to secondary amines. These novel derivatives have been evaluated for cytotoxicity against human cancer cell lines Hela, K562, and K562/AO2. The results indicated that these compounds possess superior bioactivity (IC50 values were found at the range of 10(- 6)-10(- 8) mol/l) and weak multidrug resistance.