Walnut hull (wal hull) is an agricultural by-product that iswidely used in traditionalmedicine for alleviating pain and treating skin diseases, however, recently it has gained much attention in modern pharmacology due to its antioxidant properties. The current study was aimed to determine the total phenolic, flavonoid, and tannin content of Persian wal hull extract and evaluate its biological effects on platelet function. Experimental data showed that acetone extract of wal hulls has a high content of polyphenolic compounds and antioxidant properties. The analytical study of crude extract by gas chromatographyemass spectrometry demonstrated different types of high- and low-molecular-weight compounds that are basically and biologically important. Moreover, an in vitro study revealed that wal hull extract at a concentration of 50 mg/mL inhibited thrombin-induced platelet aggregation and protein secretion by 50%, without any cytotoxic effects on platelets. The examined extract suppressed reactive oxygen species generation and also caspase activation in thrombinstimulated platelets. Identically, N-acetylcysteine inhibited the increase of reactive oxygen species level induced by thrombin in platelets, and supported a link between cellular redox status and caspase activation in activated platelets. Presumably, the antiplatelet activity of wal hull extract is related to its polyphenolic compounds and their antioxidant properties. Therefore, wal hulls can be considered as a candidate for thrombotic disorders.

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