Glycogen synthase kinase -3 (GSK-3) is a key enzyme involved in numerous physiological events and in major diseases, such as Alzheimer's disease, diabetes, cardiac hypertrophy. Indirubins are bisindoles which can be generated from various natural sources or chemically synthesized. While highly potent and selective as GSK-3 inhibitors, most indirubins exhibit low water solubility. To address the issue of solubility we have designed novel analogues of 6-bromo-indirubin-3′-oxime with increased hydrophilicity, based on the GSK-3/indirubins co-crystal structures. The new derivatives with an extended amino side chain attached at position 3′ showed potent GSK-3 inhibitory activity, enhanced selectivity and dramatically increased water solubility. Furthermore, some of them displayed little or no cytotoxicity. The new indirubins inhibit GSK-3 in a cellular reporter model. They alter the circadian period measured in rhythmically expressing cell cultures, suggesting that they might constitute tools to investigate circadian rhythm regulation.

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h Existing therapies for leishmaniases present significant limitations, such as toxic side effects, and are rendered inefficient by parasite resistance. It is of utmost importance to develop novel drugs targeting Leishmania that take these two limitations into consideration. We thus chose a target-based approach using an exoprotein kinase, Leishmania casein kinase 1.2 (LmCK1.2) that was recently shown to be essential for intracellular parasite survival and infectivity. We developed a four-step pipeline to identify novel selective antileishmanial compounds. In step 1, we screened 5,018 compounds from kinase-biased libraries with Leishmania and mammalian CK1 in order to identify hit compounds and assess their specificity. For step 2, we selected 88 compounds among those with the lowest 50% inhibitory concentration to test their biological activity on host-free parasites using a resazurin reduction assay and on intramacrophagic amastigotes using a high content phenotypic assay. Only 75 compounds showed antileishmanial activity and were retained for step 3 to evaluate their toxicity against mouse macrophages and human cell lines. The four compounds that displayed a selectivity index above 10 were then assessed for their affinity to LmCK1.2 using a target deconvolution strategy in step 4. Finally, we retained two compounds, PP2 and compound 42, for which LmCK1.2 seems to be the primary target. Using this four-step pipeline, we identify from several thousand molecules, two lead compounds with a selective antileishmanial activity.

The dialdehydes oleacein (2) and oleocanthal (4) are closely related to oleuropein (1) and ligstroside (3), the two latter compounds being abundant iridoids of Olea europaea. By exploiting oleuropein isolated from the plant leaf extract, an efficient procedure has been developed for a one-step semisynthesis of oleacein under Krapcho decarbomethoxylation conditions. Highlighted is the fact that 5-lipoxygenase is a direct target for oleacein with an inhibitory potential (IC50: 2 μM) more potent than oleocanthal (4) and oleuropein (1). This enzyme catalyzes the initial steps in the biosynthesis of pro-inflammatory leukotrienes. Taken together, the methodology presented here offers an alternative solution to isolation or total synthesis for the procurement of oleacein, thus facilitating the further development as a potential anti-inflammatory agent.