Isolation of anticancer constituents from Cucumis prophetarum var. prophetarum through bioassay-guided fractionation.

BACKGROUND: Cucumis prophetarum var. prophetarum is used in Saudi folk medicine for treating liver disorders and grows widely between Abha and Khamis Mushait City, Saudi Arabia. METHODS: Bioassay-guided fractionation and purification were used to isolate the main active constituents of Cucumis prophetarum var. prophetarum fruits. These compounds were structurally elucidated using NMR spectroscopy, mass spectral analyses and x-ray crystallography. All fractions, sub-fractions and pure compounds were screened for their anticancer activity against six cancer cell lines. RESULTS: The greatest cytotoxic activity was found to be in the ethyl acetate fraction, resulting in the isolation of five cucurbitacin compounds [E, B, D, F-25 acetate and Hexanorcucurbitacin D]. Among the cucurbitacins that were isolated and tested cucurbitacin B and E showed potent cytotoxicity activities against all six human cancer cell lines. CONCLUSION: Human breast cancer cell lines were found to be the most sensitive to cucurbitacins. Preliminary structure activity relationship (SAR) for cytotoxic activity of Cucurbitacins against human breast cancer cell line MDA-MB-231 has been reported.

Design, synthesis, and biological evaluation of steroidal analogs as estrogenic/anti-estrogenic agents.

Series of estrone based analogs were synthetically investigated at positions C-9, C-11, C-16, and C-17 positions, to be biologically evaluated via assessment of cell proliferation, cytotoxicity, and estrogenic/anti-estrogenic activity. LA-7 and LA-10 revealed their potential to exhibit inhibitory estrogenic profile. This was further validated by Estrogen Receptor-α (ER-α) and Estrogen Receptor-ß (ER-ß) competitive binding assays to reveal the high selective affinity of LA-7 towards ER-α at 5.49µM, while LA-10 did not show any binding affinity towards neither ER-α nor ER-ß; suggesting another mechanism for inhibition. This was validated by in silico molecular docking simulations of LA-7 to reveal the optimum binding affinity of LA-7 towards ER-α.

Studies toward Australifungin. A Synthesis Dilemma of Regioselective Keto-Enol Tautomerization.

Studies have advanced a stereocontrolled pathway for the synthesis of australifungin. Elaboration of the trans-fused IMDA product 4 led to the cis-diol 15, which produced the α-hydroxyenone 19 upon oxidation. Computational studies on model systems indicate that the keto-enol tautomer shown for 19 is higher in energy than the keto-enol tautomer represented by the natural product 1. The reactivity of 19 does not permit mild isomerization and subsequent deprotection to yield 1. These findings raise new questions regarding the synthesis and bioactivity of australifungin and related natural products.

Cucurbitacin D Is a Disruptor of the HSP90 Chaperone Machinery.

Heat shock protein 90 (Hsp90) facilitates the maturation of many newly synthesized and unfolded proteins (clients) via the Hsp90 chaperone cycle, in which Hsp90 forms a heteroprotein complex and relies upon cochaperones, immunophilins, etc., for assistance in client folding. Hsp90 inhibition has emerged as a strategy for anticancer therapies due to the involvement of clients in many oncogenic pathways. Inhibition of chaperone function results in client ubiquitinylation and degradation via the proteasome, ultimately leading to tumor digression. Small molecule inhibitors perturb ATPase activity at the N-terminus and include derivatives of the natural product geldanamycin. However, N-terminal inhibition also leads to induction of the pro-survival heat shock response (HSR), in which displacement of the Hsp90-bound transcription factor, heat shock factor-1, translocates to the nucleus and induces transcription of heat shock proteins, including Hsp90. An alternative strategy for Hsp90 inhibition is disruption of the Hsp90 heteroprotein complex. Disruption of the Hsp90 heteroprotein complex is an effective strategy to prevent client maturation without induction of the HSR. Cucurbitacin D, isolated from Cucurbita texana, and 3-epi-isocucurbitacin D prevented client maturation without induction of the HSR. Cucurbitacin D also disrupted interactions between Hsp90 and two cochaperones, Cdc37 and p23.

Ormeloxifene efficiently inhibits ovarian cancer growth.

Ovarian cancer continues to be a leading cause of cancer related deaths for women. Anticancer agents effective against chemo-resistant cells are greatly needed for ovarian cancer treatment. Repurposing drugs currently in human use is an attractive strategy for developing novel cancer treatments with expedited translation into clinical trials. Therefore, we examined whether ormeloxifene (ORM), a non-steroidal Selective Estrogen Receptor Modulator (SERM) currently used for contraception, is therapeutically effective at inhibiting ovarian cancer growth. We report that ORM treatment inhibits cell growth and induces apoptosis in ovarian cancer cell lines, including cell lines resistant to cisplatin. Furthermore, ORM treatment decreases Akt phosphorylation, increases p53 phosphorylation, and modulates the expression and localization patterns of p27, cyclin E, cyclin D1, and CDK2. In a pre-clinical xenograft mouse ORM treatment significantly reduces tumorigenesis and metastasis. These results indicate that ORM effectively inhibits the growth of cisplatin resistant ovarian cancer cells. ORM is currently in human use and has an established record of patient safety. Our encouraging in vitro and pre-clinical in vivo findings indicate that ORM is a promising candidate for the treatment of ovarian cancer.

Structural optimization and biological screening of a steroidal scaffold possessing cucurbitacin-like functionalities as B-Raf inhibitors.

Inhibition of the mitogen-activated protein kinase (MAPK) pathway by targeting the commonly occurring mutated B-Raf in melanoma has become a practical method for the development of drugs and drug candidates. In order to expand upon the currently reported structural scaffolds used to target the MAPK pathway, molecular docking studies led to the installation an α,ß-unsaturated ketone side chain, related to the cucurbitacin class of natural products, on to an estrone core via an aldol condensation reaction, along with installation of the Δ(9,11) olefin to assemble what has been defined as a pseudo-cis configuration at the B/C ring juncture. Combination of these cucurbitacin-like features resulted in a compound with an enhanced biological profile against the A-375 mutant B-Raf cell line, in regards to their cytotoxicity and inhibitory activity toward phosphorylated extracellular-signal-regulated kinase (ERK).

Synthesis of novel estrone analogs by incorporation of thiophenols via conjugate addition to an enone side chain.

Functionalized estrogen analogs have received interest due to their unique and differing biological activity compared to their parent compounds. The synthesis of a new class of 3-methoxyestrone analogs functionalized at the C17 position possessing both alkyl and aryl substituted α,ß-unsaturated ketones is described, along with their thiophenol conjugate addition products.

One-pot synthesis of symmetrical and unsymmetrical bisarylethynes by a modification of the sonogashira coupling reaction.

A modification of the Sonogoshira coupling reaction employing an amidine base and a substoichiometric amount of water generates symmetrical and unsymmetrical bisarylethynylenes in one pot through in situ deprotection of trimethylsilylethynylene-added intermediates.