Streptomyces avermitilis Abamectin

Abamectin is an insecticide/acaricide that contains a mixture of avermectin Bja (>80%) and avermectin Bjb (<20%) as active ingredients. Avermectins, which are macrocyclic lactones, are derived from the actinomycete, Streptomyces avermitilis (soil microorganism). It is used to control insect and mite pests of a wide range of agronomic, fruit, vegetable, and ornamental crops. It is also used by home owners for control of fire ants. It has an oral LD50 in rats of 300 mg/kg. 

Streptomyces avermitilis. The products (a mixture of the fermentation) is abamectin, the common name for products such as Avermectin , Affirm , or and Avid. ... 

Natural products can sometimes be used in crop protection following suitable chemical modification. A good example of a semi-synthetic compound is Syngenta s insecticide emamectin, prepared by synthetic modification of the natural product abamectin (= avermectin Bi) which, in turn, is obtained by fermentation of the bacterium Streptomyces avermitilis (Figure 1). Emamectin is a highly potent insecticide, used at rates as low as 5-25 g/ha, and it is this that justifies the high costs associated with its production. ... 

Ivermectin is a macrolide compound derived from abamectin, a metabolite produced by Streptomyces avermitilis. More precisely, it is a mixture of two compounds, 22,23-dihydroavermectin (80%) and 22,23-dihydroavermectin (20%) (12). It is widely... 

In the middle of the 20th century, the synthetic development of DDT and other chlorinated hydrocarbons (C.H.), increased insecticidal activity well beyond that of most natural products. Problems arose with bioaccumulation of C.H. residues in the food chain, human fat tissue, mother s milk, as well as the development of insecticide resistance. It became obvious there were limitations to synthetic technology as well. The modification of a natural product, for example, from chrysanthemum flowers and their pyrethrum extracts (7) to pyrethroids such as allethrin, resmethrin, permethrin (2), and deltamethrin created a model in which insecticides are created from the skeleton of insecticidally active natural molecules. Thus, the avermectin, abamectin, ivermectin family of pesticides originated from compounds produced by the soil bacterium, Streptomyces avermitilis (5), and the commercially successful chloronicotinyl insecticides, though not derived from nicotine, are chemically related 4). Both pyrethroids and chloronicotinyls are currently used commercially as termiticides. We have previously provided a detailed review of natural products as pesticidal agents for control of the Formosan subterranean termites, Coptotermes formosanus Shiraki (5). 

Althouj h the concern of this publication is agricultural pest mana ent, this article will review some of the animal and human he th data, since the major impact of the avermectins lies in that area, and crop protection is of secondary importance. Currently two avermectin derivatives, ivermectin and avermectin Bl, are commercially available for animal health applications. A third one, doramectin, is under development by Pfizer (FIGURE 1). Avermectin Bl, with the generic name abamectin, is the major and most important product of the fermentation of Streptomyces avermitilis. It also serves as the starting material for the chemical conversion to ivermectin via selective hydrogenation of the 22,23 double bond. Milbemycin derivatives have only recently become commercially available. Milbemycin A /A has just been introduced in Japan for crop protection,... 

---