HPLC-based activity profiling for GABAA receptor modulators in Adenocarpus cincinnatus.

In a two-microelectrode voltage clamp assay with Xenopus laevis oocytes, a dichloromethane extract of Adenocarpus cincinnatus roots and tubers (Leguminosae) enhanced the GABA-induced chloride current (IGABA) through receptors of the subtype α1β2γ2s by 126.5 ± 25.1% when tested at 100 μg/mL. By means of HPLC-based activity profiling, 15 flavonoid and isoflavonoid derivatives, including eight new compounds, were identified in the active fractions of the extract. Isoflavone 11 and pterocarpans 2 and 8 showed promising activity in the oocyte assay, with EC50 values between 2.8 ± 1.4 and 18.8 ± 2.3 μM. Maximal potentiation of IGABA ranged between 490% and 640%. This is the first report of pterocarpans as GABAA receptor modulators.