Cell cycle arrest and apoptosis induction by an anticancer chalcone epoxide.

Safe and effective chemotherapeutic agents for the treatment of pancreatic cancer remain elusive. We found that chalcone epoxides (1,3-diaryl-2,3-epoxypropanones) inhibited growth in two pancreatic cancer cell lines, BxPC-3 and MIA PaCa-2. Three compounds were active, with GI(50) values of 5.6 to 15.8 microM. Compound 4a, 1,3-bis-(3,4,5-trimethoxyphenyl)-2,3-epoxypropanone, had an average GI(50) of 14.1 microM in the NCI 60-cell-line panel. To investigate the mode of action, cell cycle analyses of BxPC-3 cells were carried out. Treatment of cells with 50 microM 4a resulted in dramatic accumulation at G2/M (61% after 12 h for 4a vs. 15% for untreated cells). The cells rapidly entered apoptosis. After 12 h, 26% of cells treated with 50 microM 4a had entered apoptosis vs. 4% for cells treated with 100 microM etoposide and 2% for untreated cells. Compound 4a interfered with paclitaxel enhancement of tubulin polymerization, suggesting microtubules as the site of action. Reaction of thiol nucleophiles with 4a under basic conditions resulted in epoxide ring-opening and retroaldol fragmentation, yielding alkylated thiol. MALDI mass spectrometry showed that retroaldol reaction occurred upon treatment of beta-tubulin with 4a. The site of alkylation was identified as Cys(354). Chalcone epoxides warrant further study as potential agents for treatment of cancer.

Methyl (Z)-2-chloro-3-(2-methoxy-carbonyl-phen-yl)prop-2-enoate.

In the title compound, C(12)H(11)ClO(4), the propenoate C=C bond is in the Z configuration. The propenoate C=O and C=C groups are essentially coplanar [C=C-C=O torsion angle = 172.4 (3)°] with the O atom synperiplanar to the Cl atom. However, the π systems of the aromatic ring and chloro-propenoate substituent are not coplanar; the corresponding dihedral angle is 51.5 (1)°. The noncoplanarity is likely due to steric inter-actions between the propenoate H atom and the ortho-methoxy-carbonyl group on the aromatic ring. Even in the observed noncoplanar conformation, the ortho C=O to H distance (2.40 Å) is less than the sum of the van der Waals radii of O and H (2.65 Å).

Emollient, humectant, and fluorescent alpha,beta-unsaturated thiol esters for long-acting skin applications.

We describe compounds in which an emollient or a humectant bears an alpha,beta-unsaturated thiol ester capable of reacting with nucleophilic amino acids in stratum corneum proteins. These compounds should serve as long-lasting moisturizers for skin. The emollient derivatized was octadecyl propanoate, and the humectant was poly(ethylene glycol). These hydrophobic and hydrophilic compounds, as well as a fluorescent, dansyl-containing thiol ester, were found to react within minutes with the thiol N-acetylcysteamine upon addition of a catalytic amount of an organic base in chloroform. The structures of the products resulting from conjugate addition to the unsaturated thiol esters were determined by NMR spectroscopy. In the case of the alpha,beta,gamma,delta-unsaturated (sorboyl) thiol ester, both the 1,4-addition product and the beta,gamma-unsaturated-1,6-addition product formed, followed by diadduct. An in vivo test of the fluorescent alpha,beta-unsaturated thiol ester showed that this compound persisted on skin for 3 weeks vs. 6 days for the non-bonding control compound.

Kinetics and mechanism of the addition of nucleophiles to alpha,beta-unsaturated thiol esters.

Compounds containing the UV-absorbing chromophores p-methoxycinnamate, p-methoxycinnamide, or anthranilate and an alpha,beta- or alpha,beta,gamma,delta-unsaturated thiol ester (crotonyl or sorboyl) have been prepared. These compounds are subject to nucleophilic attack at the C=C conjugated to the thiol ester carbonyl group. The kinetics of the reactions of these thiol esters with N-acetyl-l-cysteine (NAC), N-acetylcysteamine, and N(2)-acetyl-L-lysine (NAL) have been studied, and the thiol addition products have been identified. The reaction rates increased at higher pH, and the reaction of NAC thiolate with a crotonyl thiol ester in 1:1 (v/v) acetonitrile/aqueous HEPES exhibited buffer catalysis as a result of protonation of the enolate intermediate. At the same concentration, NAC underwent approximately 300-fold more reaction than NAL with a crotonyl thiol ester at pH 9.8. Additionally, a crotonyl thiol ester was found to be 7.9 times more reactive than a sorboyl thiol ester toward NAC addition. These unsaturated thiol esters may serve as a means of covalently binding UVA and UVB sunscreens to the outer layer of skin to provide long-lasting protection.