Synthesis and structure–activity relationships of novel, substituted 5,6-dihydrodibenzo[a,g]quinolizinium P2X7 antagonists

Iminium quaternary protoberberine alkaloids (QPA) have been found to be novel P2X7 antagonists. To assess their structure–activity relationships, these compounds were modified at their R1 and R2 groups and assayed for their ability to inhibit the 2′(3′)-O-(4-benzoylbenzoyl)-ATP (BzATP)-induced uptake of fluorescent ethidium by HEK-293 cells stably expressing the human P2X7 receptor, and their ability to inhibit BzATP-induced IL-1β release by differentiated THP-1 cells. Compounds 15a and 15d, with alkyl groups at the R1 position, and especially compound 19h, with the 2-NO2-4,5-dimethoxy-benzyl group at the R2 position, had potent inhibitory efficacy as P2X7 antagonists.

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