Three phenanthrenes (1–3), four indole alkaloids (4–7) and one steroid (8) were isolated from the leaves of Calanthe arisanensis for the first time. In the antiplatelet aggregation assay, phenanthrenes 1 and 2 showed potential antiplatelet activity. We have reported and discussed here the antiplatelet aggregation properties of the eleven naturally-occurring phenanthrenes (1–2 and 9–17) isolated from the underground part of the plant and eighteen chemically synthesized phenanthrenes (18–35). Overall, our data demonstrated that 1,4-phenanthrenequinones 20, 21 and 22 (collagen, IC50 0.2, 0.2, 0.1 μg/mL; thrombin, IC50 0.8, 1.0, 1.1 μg/mL, respectively) could be promising lead candidates for further cardiovascular disease studies.
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