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 methylglabranin 7 we re isolated from Tephrosia tepicana, T. crassifolia, T. viridiflora, T. abb ottiae, T. leiocarpa, and T. madrensis, respectively, Leguminoseae-Papilion idae, a large tropical and subtropical genus, and their in vitro effects on different photosynthetic activities were investigated. All the compounds i solated, except 1 and 3, induced a concentration-dependent inhibition of ph otophosphorylation. Compounds 2 and 4-7 interfered with the energetic metab olism of plants at the level of photosynthesis with different mechanisms of action. Compounds 2, 4, and 6 behave as Hill reaction inhibitors, and comp ounds 5 and 7 act as energy transfer inhibitors (H+-ATPase inhibitor). (C) 2001 Academic Press.