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

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