Inhibition of COX-1 and COX-2 activity by plasma of human volunteers after ingestion of French maritime pine bark extract (Pycnogenol)

There is evidence from several studies that supplementation with French maritime pine bark extract (Pycnogenol®) improves inflammatory symptoms in vivo. However, the molecular pharmacological basis for the observed effects has not been fully uncovered yet. Direct inhibitory effects of plant extracts or components upon cyclooxygenase (COX) activity have been repeatedly reported, but the question remained whether sufficiently high in vivo concentrations of bioactive compounds could be achieved in humans. The purpose of the present study was to determine a possible inhibition of the enzymatic activity of COX-1 and COX-2 by serum samples of human volunteers after intake of French maritime pine bark extract. This methodology considered that the serum samples would contain any bioavailable active principle. Therefore, we obtained blood samples before and after 5 days administration of 200 mg Pycnogenol to five healthy humans. The plasma moderately inhibited both COX-1 and COX-2 activities ex vivo. In a second approach, 10 volunteers received a single dose of 300 mg Pycnogenol. Only 30 min after ingestion of the pine bark extract the serum samples induced a statistically significant increase in the inhibition of both COX-1 (P < 0.02) and COX-2 (P < 0.002). This suggests a strikingly rapid bioavailability of bioeffective compounds after oral intake of the extract. Thus, we provide evidence that Pycnogenol exerts effects by inhibition of eicosanoid generating enzymes which is consistent with reported clinical anti-inflammatory and platelet inhibitory effects in vivo. The next challenge is to identify the active principle(s) that are rapidly bioavailable in human plasma.