Modulating effect of flavonoids and their derivatives on sarcoplasmic reticulum Ca2+-ATPase oxidized by hypochloric acid and peroxynitrite.

Objectives: Effect of rutin and its lipophilic derivatives on Ca2+-ATPase of sarcoplasmic reticulum (SERCA) oxidized by hypochloric acid and peroxynitrite was investigated to examine the role of flavonoids in SERCA activity modulation.

Methods: Ca2+-ATPase activity was measured spectrophotometrically at 37 degrees C using NADH-coupled enzyme pyruvate kinase/lactate dehydrogenase assay. SERCA was oxidized by HOCl (3 min) or ONOO- (30 s) after previous treatment with flavonoids (2 min) at 37 degrees C. Lipophilic rutin derivatives were prepared by lipase-catalyzed esterification of flavonoids with fatty acids.

Results: Both hypochloric acid (HOCl) and peroxynitrite (ONOO-) decreased ATPase activity concentration-dependently with IC50 of 50+/-10 micromol/l and 150+/-15 micromol/l, respectively. Rutin was found to have a protective effect on SERCA activity in both oxidation systems in the concentration range 5 - 250 micromol/l. Lipophilic rutin derivatives (rutin oleate, rutin linoleate, rutin linolenate) exerted inhibitory effect on ATPase activity both in the presence and absence of oxidants.

Conclusion: The results suggest that selective lipophilization of the flavonoid skeleton may represent a useful tool for SERCA activity modulation.