Isolation and effects of some garlic components on platelet aggregation and metabolism of arachidonic acid in human blood platelets

Effects of aqueous extract of garlic, of materials extracted in two organic solvents, viz., ether and chloroform in succession, and of some fractions obtained after TLC of the aqueous extract were examined on platelet aggregation induced by several aggregating agents. Their effects were also investigated on the formation of thromboxane and lipoxygenase products from endogenous arachidonic acid in intact platelets. The aqueous extract inhibited aggregation induced by all aggregating agents and so did the materials extracted in two organic solvents. Only two fractions obtained from TLC of the aqueous garlic extract were examined for effects on epinephrine- and arachidonic acid (AA)-induced aggregation; they were found to be antiaggregatory. The material extracted in ether (MEE) inhibited the incorporation of labelled AA into platelets in platelet-rich plasma. Garlic extracts (MEE and material extracted in chloroform, MEC) at higher dosage inhibited the degradation of platelet phospholipids and reduced the formation of thromboxane (TxB2) and lipoxygenase-derived products from labelled platelets. The two organic extracts at low dosage, while not affecting the degradation of platelet phospholipids, inhibited the cyclooxygenase and lipoxygenase enzymes. A concomitant increase in the amount of released AA was observed in the treated platelets. Similar effects in relation to dosage were observed with the aqueous extract of garlic.