Evaluation of Alkaloids Isolated from Ruta graveolens as Photosynthesis Inhibitors

Abstract

Eight alkaloids (<b>1</b>⁻<b>8</b>) were isolated from <i>Ruta graveolens</i>, and their herbicide activities were evaluated through in vitro, semivivo, and in vivo assays. The most relevant results were observed for Compounds <b>5</b> and <b>6</b>⁻<b>8</b> at 150 μM, which decreased dry biomass by 20% and 23%, respectively. These are significant results since they presented similar values with the positive control, commercial herbicide 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Based on the performed assays, Compound <b>5</b> (graveoline) is classified as an electron-transport inhibitor during the light phase of photosynthesis, as well as a plant-growth regulator. On the other hand, Compounds <b>6</b>⁻<b>8</b> inhibited electron and energy transfers, and are also plant-growth inhibitors. These phytotoxic behaviors based on acridone and quinolone alkaloids may serve as a valuable tool in the further development of a new class of herbicides since natural products represent an interesting alternative to replace commercial herbicides, potentially due their low toxicity.