6-Hydroxykaempferol 3,6-di-O-glucoside and 6-hydroxykaempferol 3,6,7-tri-O-glucoside can inhibit platelet aggregation induced by collagen, they also show weak inhibitory effects on the adenosine 5'-diphosphate (ADP)- induced platelet aggregation.

Four constituents, 6-hydroxykaempferol 3,6,7-tri-O-glucoside (1), 6-hydroxykaempferol 3-O-rutinoside-6-O-glucoside (2), 6-hydroxykaempferol 3,6-di-O-glucoside (6-Hydroxykaempferol 3,6-diglucoside,3), and syringin (4) were isolated from the flower of Carthamus tinctorius L. and were examined for the inhibitory effects on platelet aggregation. The platelet aggregation was monitored by a platelet aggregometer employing a laser-scattering method. The compounds were identified on the basis of NMR spectral data.