Dark chocolate inhibits platelet isoprostanes via NOX2 down-regulation in smokers

J Thromb Haemost. 2012 Jan;10(1):125-32. doi: 10.1111/j.1538-7836.2011.04558.x.


Background: Dark chocolate is reported to decrease platelet activation but the underlying mechanism is still undefined. Dark chocolate is rich in polyphenols that could exert an antiplatelet action via inhibition of oxidative stress. The aim of the present study was to assess if dark chocolate inhibits platelet reactive oxidant species (ROS) formation and platelet activation.

Methods: Twenty healthy subjects (HS) and 20 smokers were randomly allocated to receive 40 g of dark (cocoa > 85%) or milk chocolate (cocoa < 35%) in a cross-over, single-blind study. There was an interval of 7 days between the two phases of the study. At baseline and 2 h after chocolate ingestion, platelet recruitment (PR), platelet ROS, platelet isoprostane 8-ISO-prostaglandin F2α (8-iso-PGF2α), Thromboxane (TxA2) and platelet activation of NOX2, the catalytic sub-unit of NADPH oxidase, and serum epicatechin were measured.

Results: Compared with HS, smokers showed enhanced PR, platelet formation of ROS and eicosanoids and NOX2 activation. After dark chocolate, platelet ROS (-48%, P < 0.001), 8-iso-PGF2α (-10%, P < 0.001) and NOX2 activation (-22%, P < 0.001) significantly decreased; dark chocolate did not affect platelet variables in HS. No effect of milk chocolate was detected in both groups. Serum epicatechin increased after dark chocolate in HS (from 0.454 ± 0.3 nm to 118.3 ± 53.7 nm) and smokers (from 0.5 ± 0.28 nm to 120.9 ± 54.2 nm). Platelet incubation with 0.1-10 μm catechin significantly reduced PR, platelet 8-iso-PGF2α and ROS formation and NOX2 activation only in platelets from smokers.

Conclusions: Dark chocolate inhibits platelet function by lowering oxidative stress only in smokers; this effect seems to be dependent on its polyphenolic content.

Publication types

  • Controlled Clinical Trial

MeSH terms

  • Blood Platelets / drug effects
  • Blood Platelets / metabolism*
  • Cacao*
  • Case-Control Studies
  • Cross-Over Studies
  • Down-Regulation / drug effects
  • Isoprostanes / antagonists & inhibitors*
  • Membrane Glycoproteins / antagonists & inhibitors*
  • NADPH Oxidase 2
  • NADPH Oxidases / antagonists & inhibitors*
  • Oxidative Stress / drug effects
  • Reactive Oxygen Species / metabolism
  • Smoking / blood*


  • Isoprostanes
  • Membrane Glycoproteins
  • Reactive Oxygen Species
  • CYBB protein, human
  • NADPH Oxidase 2
  • NADPH Oxidases