Synthesis, biological evaluation and molecular modelling of 2,4-disubstituted-5-(6-alkylpyridin-2-yl)-1H-imidazoles as ALK5 inhibitors.

A series of 2,4-disubstituted-5-(6-alkylpyridin-2-yl)-1H-imidazoles, 7a-c, 11a-h, and 16a-h has been synthesised and evaluated for their ALK5 inhibitory activity in an enzyme assay and in a cell-based luciferase reporter assay. Incorporation of a quinoxalin-6-yl moiety and a methylene linker at the 4- and 2-position of the imidazole ring, respectively, and a m-CONH2 substituent in the phenyl ring generated a highly potent and selective ALK5 inhibitor 11e. Docking model of ALK5 in complex with 11e showed that it fitted well in the ATP-binding pocket with favourable interactions.

Antitumor activity of spinasterol isolated from Pueraria roots.

We purified phytoestrogens from Pueraria root (Pueraria mirifica from Thailand and Pueraria lobata from Korea), which is used as a rejuvenating folk medicine in Thailand and China. Dried, powdered plant material was extracted with 100% ethanol and further separated by concentration, filtration, and thin layer silica gel chromatography. Using the fractions obtained during separation, we first investigated their cytotoxicity in several cancer cell lines from various tissues. The ethanol-extracted components (PE1, PE4) had significant antiproliferative effects on breast cancer cell lines, including MCF-7, ZR-75-1, MDA-MB-231, SK-BR-3, and Hs578T. Second, we compared these results with the cytotoxic effects of known flavonoids, sterols, and coumarins from Pueraria root. The known compounds were not as effective, and occurred in a different polarity region on HPLC. Third, further separation resulted in the isolation of eight different components (Sub PE-A to -H). One of these, PE-D, affected the growth of some breast cancer cell lines (MCF-7, MDA- MB-231) in a dose- and time-dependent manner, as well as the growth of ovarian (2774) and cervical cancer cells (HeLa). Finally, a transfection assay showed that this component had an estrogenic effect similar to 17beta - estradiol, which activates both estrogen receptor alpha (ERalpha) and ERbeta. The NMR analysis determined that spinasterol (stigmasta-7, 22-dien-3beta-ol) is an active cytotoxic component of Pueraria root.

Synthesis of new glycyrrhetinic acid (GA) derivatives and their effects on tyrosinase activity.

To synthesize glycyrrhetinic acid (GA) derivatives (3, 4, 5, 10, 13, 14, 15, and 16), we first removed the ketonic group in the C-11 position, and the carboxylic function at the C-30 position was kept intact, reduced to an alcohol, or transformed to an aldehyde corresponding derivatives 10 and 13. Glycyrrhetinic acid (GA) derivatives (3, 4, 5, 15, and 16) were coupled with 4-amino piperpyridine derivatives (12 and 14) and 4-fluorobenzyl bromide at C-30 carboxylic acid position of glycyrrhetinic acid. In subsequent tyrosinase assays, we found that GA derivatives 4, 5, and 16 were not active at early time points, but strongly inhibited tyrosinase activity at late time points. Of the GA derivatives examined, derivative 5 was most active, with an IC(50) value of 50 microM after 2 h reaction. IC(50) values of derivatives 4 and 16 were 120 and 170 microM, respectively. Further kinetic data indicated that these derivatives are slow-binding inhibitors of tyrosinase. The time-dependent inhibition was reversed when vitamin C or kojic acid was used, that is, both compounds showed active inhibition at early time points. These results suggest that GA derivatives are much more stable than vitamin C or kojic acid, although their intrinsic inhibitory potentials are relatively low. Higher stability and activity suggest that GA derivative 5 might be a useful candidate for skin whitening.

Synthesis and biological activity of novel retinamide and retinoate derivatives.

Retinoic acid and its amide derivative, N-(4-hydroxyphenyl)retinamide (4-HPR), have been proposed as chemopreventative and chemotherapeutic agents. However, their low cytotoxic activity and water solubility limit their clinical use. In this study, we synthesized novel retinoid derivatives with improved cytotoxicity against cancer cells and increased hygroscopicity. Our syntheses were preceded by selective O-acylation and N-acylation, which led to the production of retinoate and retinamide derivatives, respectively, in one pot directly from aminophenol derivatives and retinoic acid without protection. Transcription assays in COS-1 cells indicated that the N-acylated derivatives (2A-5A) and 4-HPR (1A) were much weaker ligands for all three subtypes of retinoic acid receptor (RAR) than all-trans retinoic acid (ATRA), although they showed some selectivity for RARbeta and RARgamma. In contrast, the O-acylated retinoate derivatives (1B-5B) activated all three RAR isotypes without specificity to an extent similar to ATRA. The cytotoxicity was determined using an MTT assay with HCT116 colon cancer cells, and the IC(50) of N-acylated retinamide derivative 4A and O-acylated retinoate derivative 5B was 1.67 microM and 0.65 microM, respectively, which are about five and 13-fold better than that of 4-HPR (8.21 microM), a prototype N-acylated derivative. When retinoate derivative 5B was coupled to organic acid salts, the resulting salt derivatives 5C and 5D had RAR activation and cytotoxicity similar to those of 5B. These data may delineate the relationship between the structure and function of retinoate and retinamide derivatives.

Efficacy validation of synthesized retinol derivatives In vitro: stability, toxicity, and activity.

Retinol (vitamin A) is used as an antiwrinkle agent in the cosmetics industry. However, its photo-instability makes it unsuitable for use in general cosmetic formulations. To improve the photo-stability of retinol, three derivatives (3, 4, and 5) were synthesized and their biological activities were analyzed. 1H NMR and HPLC analysis indicated that derivatives 3 and 5 were much more stable than retinol under our sunlight exposure conditions. When human adult fibroblasts were treated, the IC(50) of derivative 3 was 96 microM, which is similar to that of retinol, as determined by the MTT assay. Derivatives 4 and 5 were 2.5 and 8 times more toxic than retinol, respectively. At 1 microM treatment, like retinol, derivatives 3 and 4 were specifically active for RARalpha out of six retinoid receptors (RAR/RXRalpha, beta, gamma). Dose-dependent analysis confirmed that derivative 4 was as active as retinol and the other two derivatives were less active for RARalpha. The effect of our derivatives on the expression of collagenase, an indicator of wrinkle formation, was measured using the transient co-expression of c-Jun and RT-PCR in HaCaT cells. Collagenase promoter activity, which is increased by c-Jun expression, was reduced 42% by retinol treatment. The other derivatives inhibited collagenase promoter activity similarly. These results were further confirmed by RT-PCR analysis of the collagenase gene. Taken together, our results suggest that retinol derivative 3 is a promising antiwrinkle agent based on its higher photo-stability, lower RARalpha activity (possibly indicating reduced side effects), and similar effect on collagenase expression.