Four natural products were isolated from the fungus Botryosphaeria rhodina, and their effects on photosynthesis were tested. Only lasiodiplodin (1) inhibited ATP synthesis and electron flow from water to methylviologen; therefore, it acts as a Hill reaction inhibitor in freshly lysed spinach thylakoids. Photosystem I and II and partial reactions as well as ATPase were measured in the presence of 1. Three new different sites of 1 interaction and inhibition were found: one at CF1, the second in the water-splitting enzyme, and the third at the electron-transfer path between P680 and QA; these targets are different from that of the synthetic herbicides present. Electron transport chain inhibition by 1 was corroborated by fluorescence induction kinetics studies.

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