Diverse biological activities displayed by phenothiazines, benzo[a]phenothiazines and benz[c]acridins (review)

This review summarizes our experiments which are investigating the relationship between the structure and activity of mainly phenothiazines, benzo[a]phenothiazines and benz[c]acridines. Phenothiazines had potent antiplasmid and antibacterial activities, but induced weak antimicrobial activity in vivo. Their antiplasmid activity seemed to be enhanced by Cl- or CF3- substitution at the 2C position of phenothiazines and modified by the side-chain length and hydrophobicity. Benzo[a]phenothiazines did not show any significant antiplasmid or antibacterial activity, but stimulated the differentiation of human myelogenous leukemic cell lines and natural killing activity of human peripheral blood mononuclear cells in vitro, and induced antimicrobial activity in vivo. Circuit current energy (CRE), circuit current (CC), bond current (BC), diatropic and paratropic properties of benzo[a]phenothiazines might be correlated with their biological activity. Benz[a]acridine showed both in vitro and in vivo antimicrobial activities, and carcinogenic activity for skin tumor. The carcinogenic benz[c]acridines showed out-of-phase in the L-region and their energy was accumulated in the K-region of the molecular orbitals. The results suggest the involvement of different molecular orbitals for the expression of various biological activities by phenothiazines, benzo[a]phenothiazines and benz[c]acridines.