121124-29-6

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 β₁, β₂, or β₃ subunits (IC₅₀s = 57, 210, and 49.8 nM for α₁β₁γ₂, α₁β₂γ₂, and α₁β₃γ₂ subunits, respectively), and potentiates the GABA response. Emamectin B_1a also binds to and inhibits glycine receptors (IC₅₀ = 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 B₁. It is effective against neonate S. eridania larvae in a foliage spray bioassay and when applied topically.

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.

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[1] H. MROZIK. Discovery of novel avermectins with unprecedented insecticidal activity[J]. Experientia. Supplementum, 1989, 42 1: 315-316. DOI: 10.1007/bf01951823
[2] G R DAWSON. Anticonvulsant and adverse effects of avermectin analogs in mice are mediated through the gamma-aminobutyric acid(A) receptor.[J]. Journal of Pharmacology and Experimental Therapeutics, 2000, 295 3: 1051-1060.