Isolation,structure identification and bio-assay of azadirachtin B

Azadirachtin B was isolated from azadirachtin A-rich dried powder that contained 7.920% azadirachtin A.The structure of azadirachtin B was identified.AFC50(media antifeedant concentration)in non-choice condition of azadirachtin B against 2nd instar larvae of Spodoptera litura was 2.42 μg·mL-1 treatment after 24 h.AFC50 in choice condition of azadirachtin B against 3rd instar larvae of S.litura were 0.18 μg·mL-1 and 0.22 μg·mL-1 treatment after 24 h and 48 h.AFC50 in non-choice condition of azadirachtin B against 3rd instar larvae of Pieris brassicae was 224.48 μg·mL-1 treatment after 24 h.Average deterrent rates of 50 μg·mL-1,30 μg·mL-1 and 10 μg·mL-1 azadirachtin B against Tribolium castaneum were 86.24%,85.06% and 70.83% treatment after 24 h,and were 67.70%,59.49% and 59.74% treatment after 48 h.