Avermectin chemistry and action: ester- and ether-type candidate photoaffinity probes

Area of Science:

• Neuropharmacology
• Medicinal Chemistry
• Molecular Biology

Background:

• Avermectin B1a is a highly effective anthelmintic, insecticide, and miticide.
• Its mechanism of action involves activating chloride channels by interacting with a specific nerve membrane site.
• Understanding this interaction is crucial for developing new therapeutic and pest control agents.

Purpose of the Study:

• To synthesize and characterize novel photoaffinity probes derived from Avermectin B1a.
• To evaluate the potency and binding characteristics of these probes at the Avermectin B1a nerve membrane target site.
• To facilitate further studies on the molecular interactions of Avermectin B1a.

Main Methods:

• Chemical synthesis of candidate photoaffinity probes by modifying the dioleandrosyl substituent of Avermectin B1a.
• Incorporation of phenyl moieties with azido, iodo, or hydroxy groups as terminal functionalities.
• Binding assays using radiolabeled Avermectin B1a ([3H]1) to compete with synthesized probes for the chloride channel binding site.

Main Results:

• Several synthesized photoaffinity probes demonstrated high potency.
• These probes effectively competed for the [3H]1 binding site on mouse, housefly, and fruit fly brain chloride channels.
• IC50 values for probe competition ranged from 7 to 57 nM, indicating strong binding affinity.

Conclusions:

• The developed photoaffinity probes are potent and effective tools for studying Avermectin B1a's interaction with chloride channels.
• These probes maintain high affinity for the target site, approximating the potency of the parent compound.
• The findings support the use of these probes in future research to elucidate the precise molecular mechanisms of Avermectin B1a.