Abamectin avermectin

Table 2. Biological Activity of Abamectin (Avermectin B ) Against Mites and Insects ...

Fig. 16. Chemical structure of abamectin avermectin R = C2H5, and avermectin B15, R = CH3. (Tritium label at the 5 position)... 

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. ... 

Two avermectins, abamectin (the avermectin B ) [71751 -41 -2] and ivermectin [70288-86-7] which is saturated at C22—C23, have been commercialized to date. These two marketed avermectins have been described in considerable detail (Table 1) (13). 

Avemiectin is the most effective of the averniectia family of natural products against agriculturally important insects and mites (14). It has been commercialized for agricultural use under the nonproprietary name abamectin. This mixture of avermectins contains at least 80% of avermectin (C4gH 20 and not more than 20% of avermectin B Abamectin for use in foHar spray appHcations is formulated as an emulsiftable... 

Another incentive to this screening may have arisen from the discovery of two remarkably potent families of fermentation products with insecticidal and acaricidal activity, the milbemycins and the avermectins. Abamectin (a mixture of not less than 80% avermectin and not more than 20% avermectin is already... 

Abamectin is a specific mixture of two components avermectin Bi and avermectin Bib. Both of these components possess a double bond between C22 and C23 and differ by a methylene group in the side-chain substituents on C25. The mixture containing not less than 80% avermectin Bu and not more than 20% avermectin B is known as abamectin. Abamectin has a broad spectrum of activity against nematodes, but is primarily used in agriculture as an acaricide and insecticide (46). 

Eprinomectin is derived from the natural product abamectin by conversion of the 4 -hydroxy group to the 4 -cp -A-acetyl substituent. Like abamectin, eprinomectin is a mixture of two active constituents that contain more than 90% 4 -deoxy-4 -(ep/-acetylamino)avermectin B a and less than 10% 4 -deoxy-4 - epi-acetylaminojavermectin Bib. It is indicated for treatment of internal and external parasites in beef and dairy cattle at a dosage of 0.5 mg/kg bw and is applied along the midline of the animal s back (61). 

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. 

Recently, van den Heuvel et al. [378 a] studied the bioconcentration of [ H]avermectin Bj in an 28-d uptake flow-through test with bluegill sunfish Lepomis macrochirus). Avermectin Bj (see Fig. 16), the major component of abamectin, possesses a molecular mass of 872. The molecular dimensions are 17.0 X 18.7 X 18.4 A and were determined by Nachbar (cited in [378]) by finding the smallest parallelepiped whose faces were centered on the inertial axes of the molecule and would enclose the van der Waals surface of the molecule. A van der Waals radius of 1.2 A for hydrogen was used and the atomic coordin-... 

SYNS AVID EC ABAMECTIN AFFIRM AGRIMEK AVERMECTIN B(SUB 1) TECHNICAL GRADE AVOMEC MK 936 D VERTIMEC D ZEPHYR... 

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

Avermectin (Ivermectin) (Doramectin) (Abamectin) (Eprinomectin) Mites, lice, Horn fly. Warble-fly larvae Solution (pour on) Parenteral solution (S.C. injection) Controlled-release ruminal bolus (ivermectin)... 

The avermectin family includes several analogs with different biological activities most are roughly 80 20 mixtures of isomers which are prohibitively difficult to separate. The complete synthesis of avermectin Au has been reported (7). Unmetabolized ivermectin or abamectin, and their monosaccharides and aglycones, are the major residues in meat and agricultural commodities (1). These are generally analyzed by HPLC. 

The parent compounds and the metabolites have very low aqueous, solubility. They have proven difficult to extract from some matrices the current method for ivermectin involves some 41 concentration and clean-up steps preceding HPLC (8). A Merck method for recovering abamectin residues from strawberries and formation of fluorescent derivatives for HPLC analysis has 18 separate steps (9). A recently published two-step solid-phase recovery procedure for ivermectin from serum indicates that it is possible to combine an abbreviated concentration and cleanup method with a sensitive and specific detection system in this case, liquid chromatography (10). An immunoassay for avermectins that could be interfaced with simplified residue recovery protocols is a promising solution to the intensifying demands on regulatory agencies to monitor these compounds. 

These 3-dimensional structures are shown in Figure 4. The top panel shows avermectin Bia and 22, 23 dihydroavermectin Bia, from which we can see some general features of abamectin and ivermectin that are not obvious from the 2-dimensional representation. These include the rigid, corrugated planar form of... 

The 3-dimensional molecular models of the avermectins helped us to define the subtle structural differences recognized by the MAbs, but these models must be viewed and interpreted with caution. Since we could not invoke solvent interactions, we have no way to know what the differences may be between these gas-phase representations and the conformations assumed in solution. On the other hand, data for other hydrophobic compounds, including some macrolide antibiotics, suggests that their gas-phase and solution structures are very similar, and the major differences we observed in Figure 4 were in hydrophobic parts of the molecule. For this reason, we did not attempt to model the last analog in Table I, the 4" deoxy-4"epimethylamino avermectin Bi hydrochloride, even though it was the best competitor in the EIAs, because it is far more water soluble than the others. Another concern is that the samples compared in the competition EIAs were mixtures of isomers, e.g., abamectin is actually avermectin Bia Bib 80 20. Because it is virtually impossible to obtain the purified individual isomers for the EIA or other tests of antibody specificity, we can only assume that the competition EIA results primarily reflected how each MAb bound to the maior isomer. 

Mrozik et al. [23] have identified a series of novel 4"-amino-4"-deoxyavermect-ins with excellent insecticidal activity. The most effective members of this class are 12 and 13 which show 1,500 fold higher activity than avermectin (abamectin) against beet armyworm, Spodoptera exigua and other lepidopteran larvae. 

The preparation of avermectins has been carried out by fermentation, microsomal oxidation of early fermentation compounds and by semi-synthetic methods [57,113]. Approaches to synthesize some avermectins such as abamectin [114] and ivermectin [115-117] have also been published. Recently the total synthesis of aver-mectin [118], avermectin A g [119] and the aglycones of avermectin A g and B g [120,121] have been reported. 

Chemicals Abamectin (a mixture of 80% avermectin B and 20% aver-mectin B, ) was provided by Dr. J. Mollet, Mercif Sharp Dohme Research Laboratories, Three Bridges, NJ. The sources of other compounds used in these assays are given elsewhere (15,17) ... 

Ivermectin. 22,23-Dihydroabamectin 22,23-dihydroavermectin B, 22,23-dihydro C-076B, MK-933 Cardomec Eqvalan Heartgard 30 Ivomec Mectizan Zimecterin. Semi-synthetic deriv of abamectin, q. v.. one of the avermectins, q.v Ivermectin contains at least 80% of... 

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