Maculosidine affect the PS I electron acceptors on leaf discs, it can inhibit ATP synthesis, basal, phosphorylating and uncoupled electron transport acting as Hill reaction inhibitors on spinach chloroplasts.

METHODS AND RESULTS:In the search for natural inhibitors of plant growth, we investigate the mechanism of action of the natural furoquinoline alkaloids isolated from Balfourodendron riedelianum (Rutaceae): evolitrine (1), kokusaginine (2), γ-fagarine (3), skimmianine (4) and Maculosidine (5) on the photosynthesis light reactions. Their effect on the electron transport chain on thylakoids was analyzed. Alkaloids 1, 2, 4 and 5 inhibited ATP synthesis, basal, phosphorylating and uncoupled electron transport acting as Hill reaction inhibitors on spinach chloroplasts. Alkaloid 3 was not active. The inhibition and interaction site of alkaloids 1, 2, 4 and 5 on the non-cyclic electron transport chain was studied by polarography and fluorescence of the chlorophyll a (Chl a). CONCLUSIONS: The results indicate that the target for 1 was localized on the donor and acceptor side of PS II. In addition alkaloids 2 and 5 affect the PS I electron acceptors on leaf discs.