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Podophyllotoxin, a cyclolignan natural product, has been the object of extensive chemomodulation to obtain better chemotherapeutic agents. Among the obtained podophyllotoxin derivatives, podophyllic aldehyde showed very interesting potency and selectivity against several tumoral cell lines, so it became our lead compound for further modifications, as described in this work, oriented toward the enlargement of the cyclolignan skeleton. Thus, modifications performed at the aldehyde function included nucleophilic addition reactions and the incorporation of the aldehyde carbon into several five-membered rings, such as thiazolidinones and benzo-fused azoles. The synthesized derivatives were evaluated against several types of cancer cells, and although some compounds were cytotoxic at the nanomolar range, most of them were less potent and less selective than the parent compound podophyllic aldehyde, with the most potent being those having the lactone ring of podophyllotoxin. In silico ADME evaluation predicted good druggability for most of them. The results indicate that the γ-lactone ring is important for potency, while the α,β-unsaturated aldehyde is necessary to induce selectivity in these cyclolignans.

Terpenylquinones are mixed biogenesis primary or secondary metabolites widespread in Nature with many biological activities, including the antineoplastic cytotoxicity, that have inspired this work. Here, we present a cytotoxic structure-activity relationship of several diterpenylhydroquinone (DTHQ) derivatives, obtained from the natural labdane diterpenoid myrceocommunic acid used as starting material. Different structural modifications, that changed the functionality and stereochemistry of the decalin, have been implemented on the bicyclic core through epoxidation, ozonolysis or decarboxylation, and through induction of biomimetic breaks and rearrangements of the diterpene skeleton. All the isomers generated were completely characterized by spectroscopic procedures. The resulting compounds have been tested in vitro on cultured cancer cells, showing their relevant antineoplastic cytotoxicity, with GI 50 values in the μM and sub-μM range. The rearranged compound 8 showed the best cytotoxic results, with GI 50 at the submicromolar range, retaining the cytotoxicity level of the parent compounds. In this report, the versatility of the labdane skeleton for chemical transformation and the interest to continue using structural modifications to obtain new bioactive compounds are demonstrated.

A new family of hybrids between cyclolignans related to podophyllic aldehyde, a non-lactonic cyclolignan, and purines were prepared and evaluated against several human tumour cell lines. Both fragments, cyclolignan and purine, were linked through aliphatic and aromatic chains. The influence on the cytotoxicity of the purine substitution and the nature of the linker is analyzed. The new family was slightly less cytotoxic than the parent podophyllic aldehyde, although the selectivity is maintained or even improved and among the linkers used, the presence of an aromatic ring gave the most potent and selective derivatives within the new series tested. Cell cycle and confocal studies demonstrate that these derivatives interfere with the tubulin polymerization and arrest cells at the G(2)/M phase, in the same way than the parent compounds podophyllotoxin and podophyllic aldehyde do., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)