Inhibition of Photophosphorylation and Electron Transport by Flavonoids and Biflavonoids from Endemic Tephrosia spp. of Mexico

The biflavonoids tepicanol 1 and crassifolin 2 and the flavonoids elongatin 3, tephrobotin 4, tephroleocarpin 5, glabranin 6, and methylgiabranin 7 were isolated from Tephrosia tepicana, T. crassifolia, T. viridiflora, T. abbottiae, T. leiocarpa, and T. madrensis, respectively, Leguminoseae-Papilionidae, a large tropical and subtropical genus, and their in vitro effects on different photosynthetic activities were investigated. All the compounds isolated, except 1 and 3, induced a concentration-dependent inhibition of photophosphorylation. Compounds 2 and 4-7 interfered with the energetic metabolism of plants at the level of photosynthesis with different mechanisms of action. Compounds 2,4, and 6 behave as Hill reaction inhibitors, and compounds 5 and 7 act as energy transfer inhibitors (H-ATPase inhibitor).