ISOLATION OF AN ANTIFEEDANT COMPOUND FROM ANDROGRAPHIS-PANICULATA (ACANTHACEAE) AGAINST THE DIAMONDBACK MOTH, PLUTELLA-XYLOSTELLA (LEPIDOPTERA, YPONOMEUTIDAE)

Guided by bioassay test results, we have isolated an antifeedant compo und against the diamondback moth, Plutella xylostella, from the hexane layer of the extract of Andrographis paniculata. The compound was ide ntified as 14-deoxyandrographolide. Although this compound is used as a medicine in Pharmacology, its antifeedant activity against insects h as not yet been reported. The minimum effective dose (MED) of the isol ated compound in suppressing the feeding of DBM larva was 100 mu g/lea f disc. It was less potent than crude extract of the hexane layer (MED = 30 mu g/leaf disc) and a subfraction 5-2 derived from this layer (M ED = 50 mu g/leaf disc). This result suggests that substance(s) other than 14-deoxyandrographolide are present in the hexane layer, and may also be contributing towards feeding suppression against the DBM larva . Commercially available andrographolide was also tested for its antif eedant activity and the result (MED = 25 mu g/leaf disc) showed that i t was more potent than 14-deoxyandrographolide.