Synthesis and in vitro evaluation of 8-hydroxyquinolines as dental plaque inhibitors

Some 4- and 5-substituted 8-hydroxyquinolines, with predicted log P values in the range of 1.48-2.90, were synthesized by modified Skraup reactions or thermal cyclization. These hydroxyquinolines include the 5-methyl, 4,5-dimethyl, 4-methyl, 5-hydroxy-4-methyl, 5-methoxy, 5-methoxy-4-methyl, 4-hydroxy, 4-chloro, 4-amino, and 5-amino analogs. Partition coefficients, antibacterial activity, and antiplaque activity were determined. Four analogs showed in vitro antiplaque activity. None of the derivatives with ionizable functions was active.