title: Biflavonoids isolated from Selaginella lepidophylla inhibit photosynthesis in spinach chloroplasts.
abstract: Through bioactivity-guided chemical analysis of Selaginella lepidophylla, biflavonoids robustaflavone (1), 2,3-dihydrorobustaflavone (2), and 2,3-dihydrorobustaflavone-5-methyl ether (3) were isolated and their structures confirmed by spectroscopic and spectrometric analyses. Their NMR resonances were unambiguously assigned from HMBC, NOESY, and NOESY-1D experiments, and absolute configurations of 2 and 3 were established. Compound 3 has not been reported, and although structure of 2 was described before, the (13)C NMR assignment does not correlate with the structure reported. Therefore, this is the first report of 2. All compounds inhibited ATP production. Compounds 1 and 2 behaved as Hill reaction inhibitors. 1 interacted with photosystem II, transforming the reaction centers to silent centers at 300 and 600 microM. The interaction and inhibition target of 2 was located on Cyt b6f to PC. The three compounds also behaved as energy transfer inhibitors, 3 being the most active.
authors.affiliation: Departamento de Farmacia, Facultad de Química, Universidad Nacional Autónoma de México, México DF, CP 04510, Mexico. laurents@servidor.unam.mx
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Aguilar
authors.forename: Maryosawa G
authors.initials: MG
authors.lastname: Romero
authors.forename: María Isabel
authors.initials: MI
authors.lastname: Chávez
authors.forename: Beatriz
authors.initials: B
authors.lastname: King-Díaz
authors.forename: Blas
authors.initials: B
authors.lastname: Lotina-Hennsen
mesh_terms: D044946:Biflavonoids / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D010788:Photosynthesis / Q000187:drug effects*; D045332:Photosystem II Protein Complex / Q000187:drug effects; D032503:Selaginellaceae / Q000737:chemistry*; D018724:Spinacia oleracea / Q000648:ultrastructure*
chemical_list: D044946:Biflavonoids; D004791:Enzyme Inhibitors; D045332:Photosystem II Protein Complex; C116328:robustaflavone; D017301:Ca(2+) Mg(2+)-ATPase