Thromboxane-B-2 levels in serum of rabbits receiving a single intravenous dose of aqueous extract of garlic and onion

We have shown previously that fresh garlic extract is effective in reducing thromboxane formation by platelets both in vivo and in vitro animal models of thrombosis. In the present study, the effect of different concentration s of a single dose of aqueous extracts of garlic and onion were evaluated o n serum thromboxane-B-2 synthesis in rabbits. Different concentrations of g arlic and onion were administered as single doses in the ear vein of rabbit s. Rabbits were bled before and at different intervals after the infusion o f garlic or onion extracts. Venous blood was collected and allowed to clot at 37 degreesC for 1 h. Thromboxane-B-2 level was measured in the serum by radioimmunoassay. It was observed that garlic inhibits the thrombin-induced platelet synthesis of TXB2 in a dose-and time-dependent manner. Maximum in hibition of TXB2 occurred between 0.5 h and 6 h at 25 and 100 mg kg(-1) gar lic. At 24 h post-garlic infusion TXB2 inhibition was reduced to 15 % of th e control and TXB2 levels were comparable to that of the control values at 72 h pots-garlic infusion. infusion of 100 mg kg(-1) onion extract did not elicit any inhibitory effect on TXB2 synthesis in the serum of rabbit durin g the treatment period. The rapid recovery of platelet cyclooxygenase activ ity after infusion of a single dose of garlic suggests that garlic should b e taken more frequently in order to achieve beneficial effects in the preve ntion of thrombosis. (C) 2000 Harcourt Publishers Ltd.