Cinatrin C2

Cinatrins A, B and C3 inhibited phospholipase A2 purified from rat platelets in a dose-dependent manner. Cinatrin C3, the most potent component (IC50 70 microM), was noncompetitive with a Ki value of 36 microM. Cinatrins B and C3 also inhibited both porcine pancreas and Naja naja venom phospholipase A2. Inhibition of rat platelet phospholipase A2 by cinatrin C3 was independent of Ca2+ and substrate concentration. Comparison with duramycin, another phospholipase A2 inhibitor, displayed inhibition dependent on substrate concentration when phosphatidylethanolamine was the substrate. These results indicate that the inhibition of phospholipase A2 by cinatrin C3 may result from direct interaction with the enzyme.

Cinatrins A, B, C1, C2 and C3, a family of phospholipase A2 inhibitors were isolated from the fermentation broth of Circinotrichum falcatisporum RF-641. They were found to be novel spiro-gamma-dilactones and gamma-lactones derived from 1,2,3,5-tetra or 1,2,3(or 1,2,4)-trihydroxypentadecane-1,2,3-tricarboxylic acids. Structures were elucidated by MS and NMR studies and chemical transformations. The structure of cinatrin C3 was confirmed by X-ray crystallographic analysis, and its absolute configuration was determined by comparison of the CD spectra with related compounds.