Tobacco contains nicotine, which can kill insects. Generally, waste tobacco leaves or tobacco stems are used as raw materials, and the nicotine is extracted with acid, and then formulated into nicotine pesticides.
Nicotine is the famous nicotine. It is an organic compound with the chemical formula C10H14N2. It is highly toxic. It is an alkaloid that exists in Solanaceae plants (genus Solanum) and is also an important component of tobacco. Nicotine can cause addiction or dependence, and repeated use also increases heart rate and blood pressure and reduces appetite. Large doses of nicotine can cause vomiting and nausea, and in severe cases, death. Of course, the nicotine in cigarettes is addictive and has an insecticidal effect.
The chemical name of nicotine is: (S)-3-(1-methylpyrrolidin-2-yl)pyridine or 1-methyl-2-(3-pyridyl)pyrrolidine. The main structure of neonicotinoid pesticides is based on nicotine and modified with halogen elements.
In mammals and insects, nicotine mainly acts on nicotinic acetylcholine receptors (nAChRs)
Neonicotinoid insecticides mainly act on nicotinic acetylcholine receptors (nAChRs) on the postsynaptic membrane of insects. Acetylcholine is an endogenous agonist of the insect nervous system that stimulates neurotransmitters.
Neurotransmitters pass through the synapse of nicotinic choline in two steps: first, vesicles in the presynaptic membrane release acetylcholine, and acetylcholine binds to receptors on the postsynaptic membrane; second, changes in the conformation of the receptor molecules cause The development of ion channels promotes the inward flow of extracellular Na+ and the outward flow of intracellular K+, thereby breaking the balance of membrane potential. ) Neonicotinoid insecticides can cause insects to lose control of their movements, tremble, become paralyzed and even die. At sublethal concentrations, it can cause feeding aphids to convulse, reduce honeydew discharge, and eventually starve to death.
Neonicotinoid pesticides are actually a new type of pesticide developed, screened and synthesized based on the structural research of nicotine (started in 1904). Both neonicotinoids and nicotinic insecticides act as agonists on postsynaptic nicotinic acetylcholine (nAChRs).
However, there is a big difference in the toxicity between neonicotinoids and nicotine pesticides. Compared with nicotine pesticides, neonicotinoids are less toxic to mammals and have good effects on the nervous system of insects. Selectivity. It also has the effects of contact killing, gastric poisoning, systemic absorption, antifeeding and repellent effects; it is especially effective against sucking mouthpart pests such as aphids, leafhoppers and coleopteran pests.