Sandy Desrat

Pro-apoptotic meiogynin A derivatives that target Bcl-xL and Mcl-1

The biological evaluation of a natural sesquiterpene dimer meiogynin A 1, is described as well as that of five non-natural analogues. Although active on a micromolar range on the inhibition of Bcl-xL/Bak and Mcl-1/Bid interaction, meiogynin A 1 is not cytotoxic on three cell lines that overexpress Bcl-xL and Mcl-1. Contrarily, one of its analogues 6 with an inverted configuration on the side chain and an aromatic moiety replacing the cyclohexane ring was active on both target proteins, cytotoxic on a micromolar range and was found to induce apoptosis through a classical pathway.

Dual inhibitors of the pro-survival proteins Bcl-2 and Mcl-1 derived from natural compound meiogynin A

Thirty analogues of natural meiogynin A, a pan-Bcl-2 inhibitor, were prepared in order to elaborate cytotoxic compounds on specific cancer cells overexpressing one or more proteins of the Bcl-2 family. The interaction of all the new analogues with Bcl-xL, Mcl-1 and Bcl-2 proteins was first evaluated by fluorescence polarization assay (FPA) and showed that modulation of the lateral chain has a dramatic impact as subtle changes significantly modify the activity on the target proteins. The acetoxymethyl prodrugs of the two most active compounds were then elaborated to determine their cytotoxicity on B cell lines. A strong cytotoxic effect on BL2, RS4;11 and H929 cells was observed with a triazole prodrug that induces apoptosis.

Searching for original natural products by molecular networking: detection, isolation and total synthesis of chloroaustralasines

With the aim of isolating structurally original natural products, a molecular networking (MN)-based prioritisation approach has been developed and applied to a collection of 292 plant extracts. It led to the selection of a sample-specific cluster of ions detected in the bark extract of Codiaeum peltatum. The MN-guided purification of the targeted compounds afforded four unprecedented chlorinated monoterpenyl quinolones named chloroaustralasines A–C and isochloroaustralasine A. Faced with inconsistent spectral data of some previously reported quinolones, the total synthesis of the corresponding dihydroxy and chlorohydrin compounds was undertaken. The desired products were obtained in three steps, allowing the structural reassignment of two erioaustralasines. The chloroperoxidase-mediated hydroxychlorination reaction developed for the synthesis of the chlorinated quinolone showed that such complex molecules could be good substrates for this enzyme and, at the same time, raised the question of the biosynthetic origin of the non-artefactual chlorohydrin moiety.

Structurally Diverse Diterpenoids from Sandwithia guyanensis

Bioassay-guided fractionation of an EtOAc extract of the trunk bark of Sandwithia guyanensis, using a chikungunya virus (CHIKV)-cell-based assay, afforded 17 new diterpenoids 1-17 and the known jatrointelones A and C (18 and 19). The new compounds included two tetranorditerpenoids 1 and 2, a trinorditerpenoid 3, euphoractines P-W (4-11), and euphactine G (13) possessing the rare 5/6/7/3 (4-7), 5/6/6/4 (8-11), and 5/6/8 (13) fused ring skeletons, sikkimenoid E (12), and jatrointelones J-M (14-17) possessing jatropholane and lathyrane carbon skeletons, respectively. Jatrointelones J (14) and M (17) represent the first naturally occurring examples of C-15 nonoxidized lathyrane-type diterpenoids. The structures of the new compounds were elucidated by NMR spectroscopic data analysis. The relative configuration of compound 16 and the absolute configurations of compounds 3-6 and 14 were determined by single-crystal X-ray diffraction analysis. In addition, jatrointelone K (15) was chemically transformed to euphoractine T (8) supporting the biosynthetic relationships between the two types of diterpenoids. Only compound 15 showed a moderate anti-CHIKV activity with an EC50 value of 14 μM. Finally, using a molecular networking-based dereplication strategy, several close analogues of 12- O-tetradecanoylphorbol-13-acetate (TPA), one of the most potent inhibitors of CHIKV replication, were dereplicated.