INSECTICIDAL ALKALOIDS FROM CORYDALIS-BULBOSA AGAINST DROSOPHILA-MELANOGASTER

A MeOH extract of tubers of Corydalis bulbosa had insecticidal activit y against larvae of Drosophila melanogaster Meigen. Four protoberberin e alkaloids, (-)-tetrahydroberberine (1), (-)-tetrahydrocopticine (2), (+)-corydaline (3), (+/-)-tetrahydropalmatine (4) and (+/-)-dehydroco rydaline (5) as its iodide were isolated from the extract. Compounds 5 , 1 and 2 exhibited LC50 values toward larvae of D. melanogaster of 0. 23 mu mol/mL, 0.91 mu mol/mL and 1.70 mu mol/mL diet concentration, re spectively. Against adults, 1 showed the most potent activity with an LD50 value of 2.5 mu g/adult. 1, 2, 3 and 4 inhibited acetylcholineste rase by 78.7, 71.8, 68.2 and 64.6%, respectively, at 1.0mM. Furthermor e, 5 showed the most potent activity with inhibition of 61.3% at 0.40 mM. 5, 1 and 2 were identified as insecticidal compounds from C. bulbo sa. Investigation of the structure-activity relationship indicated the importance of the methylenedioxyl group and double bonds in the isoqu inolizine moiety for enhanced activity of the protoberberine alkaloids .