A Fluoro Derivative of Embelin, as Potent B-RAF Inhibitor in Melanoma

Background: Melanoma is one of the common forms of skin cancer and B-RAF is a mutated protein found in most Melanomas. The important function of B-RAF is normal cell growth and survival. Most of known B-RAF mutations are V600E mutations. Vemurafenib is the currently used fluorine based drug used for V600E mutations but this drug has side effects, so in this scenario, more potent drugs with less side effects are required. Objective: This study aims to develop a more effective lead compound as B-RAF inhibitor from a hydroxyquinone, by structural modification of embelin, a naturally occurring hydroxybenzoquinone, which has got a potency of detoxifying blood, hence useful in wide range of skin diseases. Thus a fluorine substituted semisynthetic derivative of embelin, 5-(3-chloro-4-trifluoromethoxy phenyl amino)-2- hydroxy-3-undecyl- [1, 4] benzoquinone to fight against skin cancer was prepared. Method: Fluoro derivative of embelin was synthesized by the direct condensation of embelin with 3-chloro-4-trifluoromethoxy aniline. The structure of the product was characterized using various spectral data, obtained from IR, 1H NMR, 19F NMR, 13C NMR and Mass spectrum. Various in vitro studies like Antiproliferative study in A375 Cell Lines, (B-RAF Elisa), Western Blotting analysis, Gene Expression study by Reverse Transcriptase PCR, Caspase assay, Flow Cytometry analysis, Clonogenic assay and Transwell Migration assay were carried out to find its biological activity. Results: A semisynthetic derivative of embelin 5-(3-chloro-4-trifluoromethoxy phenyl amino)-2-hydroxy-3-undecyl- [1, 4] benzoquinone (EOCF) was prepared and the structure of the derivative was confirmed by spectral analysis. The MTT assay proves that the fluoro derivative of embelin exhibited better anticancer activity in Melanoma cell lines than the parent compound, embelin. Western blot analysis showed that B-RAF expression level was reduced by the addition of derivative than the parent compound embelin. The Caspase ELISA analysis indicated that the derivative was found to be a good apoptotic marker and from the flow cytometry analysis, it was observed that the cell arrest occurs at G0/G1 phase. Its antimetastatic activity determined using Clonogenic assay indicated that the derivative, EOCF inhibits the metastatic effects in melanoma cell lines. Migratory potential of Melanoma cells were significantly reduced in presence of EOCF when Transwell migration assay was conducted. Conclusion: This work established that the potency of the synthesized compound was more than the parent compound, embelin when it was structurally modified with 3-chloro-4-trifluoromethoxy aniline and that the derivative can be used as a lead molecule for further drug discovery.

Synthesis of purines and adenines containing the hexafluoroisopropyl group

Several new derivatives of adenine, purine, and theophylline containing the (CF3)2CH group connected to a nitrogen atom of the imidazole ring were prepared by the reaction of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (1) with the corresponding substrates, resulting in the selective alkylation of one of the nitrogen atoms of the imidazole ring. The reaction proceeds under mild conditions in a polar solvent, giving the alkylated products in 47–78% yield. While for purine and 4- and 5-azabenzimidazole, the reaction led to a mixture of two isomers, the reaction of adenine and the corresponding 2-fluoro derivative was regioselective, resulting in the formation of only one isomer in each case. The alkylation of theophylline led to the formation of a new derivative of caffeine.

Synthesis and enzymatic ketonization of the 5-(halo)-2-hydroxymuconates and 5-(halo)-2-hydroxy-2,4-pentadienoates

5-Halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates are stable dienols that are proposed intermediates in bacterial meta-fission pathways for the degradation of halogenated aromatic compounds. The presence of the halogen raises questions about how the bulk and/or electronegativity of these substrates would affect enzyme catalysis or whether some pathway enzymes have evolved to accommodate it. To address these questions, 5-halo-2-hydroxymuconates and 5-halo-2-hydroxy-2,4-pentadienoates (5-halo = Cl, Br, F) were synthesized and a preliminary analysis of their enzymatic properties carried out. In aqueous buffer, 5-halo-2-hydroxy-2,4-pentadienoates rapidly equilibrate with the β,γ-unsaturated ketones. For the 5-chloro and 5-bromo derivatives, a slower conversion to the α,β-isomers follows. There is no detectable formation of the α,β-isomer for the 5-fluoro derivative. Kinetic parameters were also obtained for both sets of compounds in the presence of 4-oxalocrotonate tautomerase (4-OT) from Pseudomonas putida mt-2 and Leptothrix cholodnii SP-6. For 5-halo-2-hydroxymuconates, there are no major differences in the kinetic parameters for the two enzymes (following the formation of the β,γ-unsaturated ketones). In contrast, the L. cholodnii SP-6 4-OT is ≈10-fold less efficient than the P. putida mt-2 4-OT in the formation of the β,γ-unsaturated ketones and the α,β-isomers from the 5-halo-2-hydroxy-2,4-pentadienoates. The implications of these findings are discussed. The availability of these compounds will facilitate future studies of the haloaromatic catabolic pathways.

Curved crystal morphology, photoreactivity and photosalient behaviour of mononuclear Zn(II) complexes

A dramatic effect of crystal morphology, photoreactivity and photosalient property is observed in a zinc(II) complex due to solvent effects and fluorine substitution at the backbone of the ligand. Of the two crystal forms with a 3-fluoro derivative, one yielded a curved morphology of single crystals and the second form shows photoreactivity in the solid state, whereas crystals of the 2-fluoro derivative pop during the [2 + 2] photocycloaddition reaction. This is the first report documenting curved single crystals of metal complexes obtained naturally during crystallization, although such bent crystals have been observed in extended solids naturally, or bent by mechanical force or by UV irradiation.