4.8. Antiplatelet Aggregation Activity
The MEZZ, together with another 48 methanol extracts of 37 species of Malaysian medicinal plants, were investigated for their ability to inhibit platelet-activating factor (PAF) receptor-binding effects using rabbit platelets [48]. At the concentrations of 18 μg/mL, the MEZZ produced approximately 96.4% inhibitory effect, which is the highest as compared to the other plants’ extracts, with Boesenbergia pandurata’s extract being the only plant with closest inhibitory effect (80.4%). Interestingly, the inhibitory effect of MEZZ was greater than Cedrol, a known PAF antagonist (85.2%), which was used as the standard drug. The IC50 value obtained for the active MEZZ was 1.2 ± 2.0 μg/mL, which was the lowest compared to Cedrol (2.4 ± 1.3 μg/mL) and B. pandurate (8.6 ± 2.6 μg/mL).
The MEZZ was also reported to exhibit strong antiplatelet aggregation activity at 100 μg/mL in human whole blood in vitro, with all extracts exhibiting 100% inhibition [49]. ASA, used as a positive control at the concentration of 25 μg/mL, exhibited inhibitory effects of 100%, 31% and 43% against arachidonic acid-, collagen- and ADP-induced platelet aggregation. Interestingly, compound isolated form RZZ, zerumbone, at the concentration of 100 μg/mL, exerted strong inhibition on platelet aggregation induced by arachidonic acid, collagen and ADP with inhibitory effects of 100%, 68%, and 100%, respectively.