Pycnogenol® and Ginkgo biloba extract: effect on peroxynitrite-oxidized sarcoplasmic reticulum Ca2+-ATPase
The effect of two natural standardized plant extracts, Pycnogenol® and EGb 761, on sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity and posttranslational modifications induced by peroxynitrite was investigated to assess their possible protective role. EGb 761 was found to have a protective effect on SERCA activity in the concentration range of 5-40 μg/ml. On the other hand, Pycnogenol® caused a decrease of SERCA activity at concentrations of 25 μg/ml. EGb 761 did not prevent protein carbonyl formation upon oxidation with peroxynitrite. On the contrary, Pycnogenol® at the concentrations of 5 and 10 μg/ml significantly decreased the level of protein carbonyls by 44% and 54%, respectively. Neither Pycnogenol® nor EGb 761 exerted a protective effect against thiol group oxidation. The plant extracts studied modulated peroxynitrite-injured SERCA activity by different ways and failed to correlate with posttranslational modifications. Their effect seems to be associated with their ability to change SERCA conformation rather than by their antioxidant capacity.