Biochemical and physiological effects of benzheterocycles and related compounds.

The biochemical and physiological effects of 18 benzheterocycles and 1 tetrahydrophthalimide-substituted indolin-2(3H)-one were investigated. Eighteen of the compounds were inhibitors of protoporphyrinogen oxidase (Protox) in vitro, with I 50 values ranging from 25 to 650 nM. There was a good correlation between the activity of these compounds as in vitro Protox inhibitors and their in vivo effects on protoporphyrin IX (Proto IX) accumulation. There was also a good correlation between the amount of Proto IX caused to accumulate and the light-induced cellular damage. However, several of the compounds had phytotoxic activity in darkness, indicating that they have mechanisms of action in addition to inhibition of Protox. Greenhouse results generally agreed with laboratory results. The structure/activity relationships for inhibition of Protox are discussed.