Effect of lichen metabolites on thylakoid electron transport and photophosphorylation in isolated spinach chloroplasts

Investigation of the lichen Parmotrema tinctorum led to the isolation of se veral known compounds. Among them, lecanorin (1), methyl-beta -orcinol carb oxylate, methyl orsellinate, orcinol, and methyl haematommate (3) caused si gnificant inhibition of the radicle growth and germination of seedlings of Amaranthus hypochondriacus and Echinochloa crusgalli. In addition, lecanori n (1) and gyrophoric acid (2) significantly inhibited the light-dependent s ynthesis of ATP and uncoupled electron transfer on the reducing side of pho tosystem II in freshly lysed, illuminated spinach chloroplasts. The targets of 1 and 2 were located at the water-splitting enzyme level and in one of the redox enzymes in the range of electron transport from P-680 to Q(A), re spectively.