Description
Emamectin B
1a is a semisynthetic derivative of avermectin B
1a . It binds to GABA
A receptors (K
i = 17.6 nM in rat brain membranes), including those containing β
1, β
2, or β
3 subunits (IC
50s = 57, 210, and 49.8 nM for α
1β
1γ
2, α
1β
2γ
2, and α
1β
3γ
2 subunits, respectively), and potentiates the GABA response. Emamectin B
1a also binds to and inhibits glycine receptors (IC
50 = 218 nM in rat spinal cord). Emamectin B
1a induces mortality in 90% of
S. exigua larvae in a diet incorporation assay at a dose of 1.067 ng/ml, which is approximately 1,500-fold more toxic than avermectin B
1. It is effective against neonate
S. eridania larvae in a foliage spray bioassay and when applied topically.
Uses
Emamectin B1a is a semi-synthetic 4”-epimethylamino analogue of avermectin B1a prepared by oxidation of the 4”-hydroxy moiety and reductive amination. The introduction of the methylamino group greatly enhances the insecticidal potency of the avermectin class. Emamectin B1a, as a benzoate salt, is the major component (>90%) of the commercial insecticide/acaricide, emamectin. Members of the avermectin/milbemycin class exert their insecticidal/anthelmintic effects by binding to glutamate-gated chloride channels expressed on nematode neurones and pharyngeal muscle cells.
