Inhibitory effects of Bulnesia sarmienti aqueous extract on agonist-induced platelet activation and thrombus formation involves mitogen-activated protein kinases

Ethnopharmacological relevance: B. sarmienti has long been recognized in folk medicine as a medicinal plant with various medicinal uses. Traditionally, it has been appreciated for the skin-healing properties of its essence. The bark has also been employed to treat stomach and cardiovascular disorders and reported to have antitumor, antioxidant and anti-inflammatory activities. However, information on its antiplatelet activity is limited. Aim of the study: To examined the effects of B. sarmienti aqueous extract (BSAE) in platelet physiology. Materials and methods: The anti-platelet activity of BSAE was studied using rat platelets for in vitro determination of the extract effect on agonist-induced platelet aggregation, ATP secretion, [Ca²⁺]_i mobilization and MAP kinase phosphorylation. The extract in vivo effects was also examined in arterio-venous shunt thrombus formation in rats, and tail bleeding time in mice. Result: HPLC chromatographic analysis revealed that B. sarmienti extract contained (+)-catechin (C), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), and (-)-epicatechin gallate (ECG). BSAE, significantly and dose dependently, inhibited collagen, thrombin, or ADP-induced platelet aggregation. The 50 percent inhibitory concentrations (IC₅₀) of the extract for collagen, thrombin and ADP-induced platelet aggregation were 45.3±2.6, 100±5.6 and 110±4.6μg/ml, respectively. Collagen activated ATP release and thrombin-induced intracellular Ca²⁺ concentration were reduced in BSAE-treated platelets. In addition, the extract in vivo activity showed that BSAE at 100mg/kg significantly attenuated thrombus formation in rat extracorporeal shunt model while mice tail bleeding time was not affected. Moreover, BSAE attenuated p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase 1 (JNK1) and extracellular-signal-regulated protein kinase 2 (ERK2) phosphorylations. Conclusion: BSAE inhibits platelet activation, granule secretion, aggregation, and thrombus formation without affecting bleeding time, and that this effect is mediated by inhibition of P38, JNK1 and ERK2 phosphorylations. The ability of BSAE to inhibit platelet function might be relevant in cases involving aberrant platelet activation where the plant extract could be considered as a candidate to anti-platelet and antithrombotic agent.