Antihyperglycaemic flavonoids from Syzygium samarangense (Blume) Merr. and Perry

2′,4′‐Dihydroxy‐3′,5′‐dimethyl‐6′‐methoxychalcone 1, its isomeric flavanone 5‐O‐methyl‐4′‐desmethoxymatteucinol 2 and 2′4′‐dihydroxy‐6′‐methoxy‐3′‐methylchalcone 3 were isolated from the leaves of S. samarangense using a bioassay‐directed scheme. In an oral glucose tolerance test, at a dosage of 1.0 mg[sol ]20 g mouse, 1 and 2 significantly ( α = 0.05) lowered the blood glucose levels (BGLs) in glucose‐hyperglycaemic mice when administered 15 min after a glucose load. When co‐administered with glucose, only 1 showed a significant lowering of BGLs 45 min after its oral administration. When administered 15 min before glucose, none of the flavonoids showed a positive effect. Only 1 decreased significantly, at α = 0.05, the BGLs of alloxan‐diabetic mice at t = 90–150 min. Copyright © 2005 John Wiley & Sons, Ltd.