Application of Abamectin
Abamectin, also known as avermectin or abameiding, is an antiparasitic, belonging to sixteen carbon ring macrolide antibiotics and extracting from metabolites of the fermentation of the afoman bacterial. It was separated out in Kitasato of Japan in 1975. Studies later found that it has a good effect on nematodes and arthropods. Over the past decade, abamectin insecticide is more widely used in animal and plant insecticide.
Abamectin drugs include abamectin, synthetic derivatives of ivermectin and doramectin. Abamectin’s mechanism is to stimulate arthropods and nematodes to release a neurotransmitter called aminobutyric acid (GABA), so the parasites are paralysed. Parasites and more advanced animals with this neurotransmitter are subjected to the paralysis by avermectin. But, it may be invalid for parasites without such neurotransmitter. Therefore, avermectin has mainly effect on nematodes and ectoparasites of higher animals, while is invalid for flukes and tapeworms. This is a defect of abamectin efficacy.
Abamectin is not a single substance, but a mixture of a class of chemical substance with similar structure produced by afoman bacterial fermentation. Currently, the abamectin products mainly contain eight components, including A1a, A1b, A2a, A2b, B1a, B1b, B2a, B2b, etc. Among them, abamectin B1 is the main component, and B1a of the B1 abamectin is the dominant component. Metabolites of afoman bacteria are not all avermectin during the fermentation process, but also other kinds of substance. Currently, researches on these substances are not enough, so most of them do not be identified clear. Some of these substances are harmful to higher animals and human. So far, there are at least two components with toxicity —- one can cause suffocation of animals, the other is possibly carcinogenic. Therefore, other substances but avermectin are removed in the process of extracting the avermectin.
Abamectin is white or light yellow crystalline powder, and is odorless. Besides, it is almost insoluble in water, slightly soluble in ethanol, and soluble in chloroform. Avermectin preparation is not stable enough and easily oxidized. Its energy decreases more quickly, especially in powders and premixes. However, avermectin injections are more stable because drugs don’t directly contact with the oxygen in the air.
At present, abamectin products developed on the market are ivermectin and doramectin. In addition, China is being developed the emamectin which not be put on the market yet. Ivermectin is made of avermectin B1a through artificially structural transformation, with avermectin as its precursors. Ivermectin is obtained by hydrogenation reduction on the double bonds between the 22nd and 23rd carbon atoms of macrolide structure of avermectin B1a. Chine requires that ivermectin raw materials shall contain more than 80% of dihydro avermectin B1a and less than 20% of dihydro avermectin B1b.
Compared with avermectin, ivermectin has stronger stability and oxidation resistance due to the double bond hydrogenation to saturated state, so it has more reliable efficacy. Meanwhile, toxicity of ivermectin is only about half of the toxicity of avermectin B1, so it has higher safety performance and its price is twice as high as avermectin.