SEVERAL ANTIFEEDANTS FROM NEEM OIL, AZADIRACHTA-INDICA A JUSS, AGAINST RETICULITERMES-SPERATUS KOLBE (ISOPTERA, RHINOTERMITIDAE)

A methanol extract of neem oil indicated antifeedant activity at 200 mug/disc by a no-choice bioassay against Reticulitermes speratus Kolbe. The extract was purified by recycling HPLC to isolate 11 compounds of variable termite antifeedant potency. Deacetylgedunin was the most active compound (95% protective concentration or PC95 = 113.7 mug/disc). This was followed by salannin, gedunin, 17-hydroxyazadiradione, nimbandiol, azadiradione, deacetylsalannin, and deacetylnimbin, with PC95 estimates of 203.3, 218.4, 235.6, 245.4, 827.5, 1373.1, and 1581.2 mug/disc, respectively. Epoxyazadiradione, 17-epiazadiradione, and nimbin were not active (PC95 estimates were beyond the bioassay limits). It could be presumed, by comparing their structures and activities, that the furan ring, alphabeta-unsaturated ketone and hydroxyl group each played an important role in determining the antifeedant activity.