Isoflavones from Camphorosma lessingii Inhibit the Organic Anion Transporters OAT1 and OAT3

Phytochemical investigation of Camphorosma lessingii has resulted in the isolation of four previously unreported isoflavones ( 1 - 4 ) and eight known compounds ( 5 - 12 ). Nine of these compounds ( 1 - 6, 8 - 10 ) are reported for the first time from members of the family Amaranthaceae. The structures of all isolated compounds were determined by spectroscopic methods, primarily one-dimensional and two-dimensional nuclear magnetic resonance and mass spectrometry. The absolute configuration of 6 was confirmed by circular dichroism. Inhibition of the organic anion transporters, OAT1 and OAT3, by the isolated compounds was evaluated. Among them, 7, 2-dihydroxy- 6,8-dimethoxyisoflavone ( 1 ), 2-hydroxy-6,7,8-trimethoxyisoflavone ( 2 ), 6,2-dihydroxy-7,8-dimethoxyisoflavone ( 3 ), and 7-methoxyflavone ( 5 ) showed a significant inhibitory effect on 6-carboxyfluorescein uptake mediated by OAT1 and OAT3.