Initial Catalyst−Substrate Association Step in Enyne Metathesis Catalyzed by Grubbs Ruthenium Complex Probed by Time-Dependent Fluorescence Quenching

This communication introduces an FRET-based simple and efficient method for monitoring kinetics and thermodynamics of organic reactions and describes its application to studies on the initial catalyst-substrate association step in the enyne metathesis catalyzed by a Grubbs Ru complex to probe the reaction initiation on the alkyne versus the alkene. The kinetic and thermodynamic parameters of alkene and alkyne with the first generation Grubbs Ru complex, determined by the time-dependent fluorescence quenching of the dye-conjugated substrate by the Ru catalyst, strongly support the dominance of the reaction initiation on alkene over alkyne in the reaction both kinetically and thermodynamically.1122sciescopu

Antiproliferative Effect of Sterols from Resin of Commiphora habessinica

Commiphora habessinica resin is used traditionally to treat various diseases in Ethiopia. In this study the cytotoxic effects of chloroform fraction and cholesterol and lathosterol isolated from the chloroform fraction of the resin of C. habessinica were evaluated. In the cytotoxicity assay on A549, A2780, MIA-Paca-2, and SNU-638 cell lines, the chloroform fraction showed cytotoxicity ranging from 0.77-3.35 ?g/ml. The chloroform fraction significantly inhibited cell proliferation of A549, A2780, MIA-PaCa-2 and SNU-638, with dose-dependent relation in vitro. The chloroform fraction was more sensitive and has a strongest net growth as percent control effects on A549 cell lines. A mixture of cholesterol : lathosterol (47.9% : 52.1%) exhibited a moderate cytotoxicity which is greater than the individual compound towards A549 and A2780 with IC50 of 13.77 and 20.36 ?g/ml, respectively that might be due to synergetic effect. The GC-MS analysis of chloroform fraction of the resin showed presence of pentacyclic triterpenes as major component (62.98%), sesquiterpene (4.27%), phytosterols (1.53%) and others in trace amount. The isolated compounds from the chloroform fraction were analysed by spectroscopic techniques such as NMR and MS

Anti-proliferative activity of a novel tricyclic triterpenoid acid from Commiphora africana resin against four human cancer cell lines

Myrrh, a resin derived from the damaged bark of Commiphora genus, has traditionally been used for treatment of various human diseases, such as amenorrhea, ache, tumors, fever, and stomach pains. In spite of this widespread use of the myrrh in Ethiopia, the pharmacological activity and chemical composition have not been studied in detail. A new tricyclic triterpene acid (3S,4S,14S,7E,17E,21Z)-3,30-dihydroxypodioda-7,17,21-trien-4-carboxylic acid (commafric A) has been isolated from a crude methanolic extract of Commiphora africana (A. Rich.) Engl. resin along with the known pentacyclic triterpene α-amyrin. The structure of commafric A was characterized using diferent spectroscopic techniques such as 1D and 2D NMR, IR, and VCD combined with computations. The anti-proliferative activity of both isolated compounds was evaluated using SRB based colorimetric cellular assay against four human cancer cell lines. Etoposide was used as a positive control. Commafric A showed signifcant anti-proliferative efects against non-small cell lung cancer (A549) with IC50 values of 4.52 μg/ml. The pentacyclic triterpene α-amyrin showed a weak antiproliferative activity against A2780 (ovarian cancer), MIA-PaCa-2 (pancreatic cancer), and SNU638 (stomach cancer) cell lines tested with IC50 values ranging 9.28 to 28.22 μg/ml. Commafric A possessed anti-proliferative activity against non-small cell lung cancer (A549), which suggests that commafric A has potential to be further optimized being a lead compound in the search for new drugs against cancer diseases