Two insecticidal tetranortriterpenoids from Azadirachta indica

Area of Science:

• Natural Products Chemistry
• Medicinal Chemistry
• Entomology

Background:

• Azadirachta indica (neem) is a source of bioactive compounds.
• Triterpenoids are a class of natural products with diverse biological activities.
• Mosquito-borne diseases pose a significant global health threat.

Purpose of the Study:

• To isolate and characterize new triterpenoids from Azadirachta indica.
• To evaluate the insecticidal activity of isolated compounds against mosquito larvae.
• To contribute to the development of novel mosquito control agents.

Main Methods:

• Methanolic extraction of fresh Azadirachta indica leaves.
• Isolation and purification of triterpenoids using chromatographic techniques.
• Structure elucidation using advanced spectroscopic methods (2D-NMR: COSY-45, NOESY, HMQC, HMBC).
• Bioassays to determine larvicidal toxicity (LC50) against Aedes aegypti larvae.

Main Results:

• Two new triterpenoids, 6 alpha-O-acetyl-7-deacetylnimocinol and meliacinol, were isolated and structurally characterized.
• 6 alpha-O-acetyl-7-deacetylnimocinol exhibited significant larvicidal activity against Aedes aegypti larvae with an LC50 of 21 ppm.
• Nimocinol, previously isolated from the same source, showed moderate larvicidal activity (LC50 = 83 ppm).
• Meliacinol demonstrated no significant toxicity against Aedes aegypti larvae up to 100 ppm.

Conclusions:

• The study identified novel triterpenoids from Azadirachta indica with potential as mosquito larvicides.
• 6 alpha-O-acetyl-7-deacetylnimocinol represents a promising candidate for developing new strategies against Aedes aegypti.
• Further research is warranted to explore the mechanism of action and optimize the application of these compounds.