Extracts from plants used in mexican traditional medicine activate Ca2+-dependent chloride channels in Xenopus laevis oocytes

Summary The two-electrode voltage-clamp technique was employed to investigate the effects of chloroform-methanol (1:1) extracts derived from five medicinal plants on Xenopus laevis oocytes. When evaluated at concentrations of 1 to 500 μg/ml, the extracts prepared from the aerial parts of Baccharis heterophylla H.B.K (Asteraceae), Chenopodium murale L. (Chenopodiaceae), Desmodium grahami Gray (Leguminosae) and Solanum rostratum Dun (Solanaceae) produced concentration-dependent oscillatory inward currents in the oocytes, while the extract of Gentiana spathacea did not induce any response. The reversal potential of the currents elicited by the active extracts was –17 ± 2mV and was similar to the chloride equilibrium potential in oocytes. These ionic responses were independent of extracellular calcium. However, they were eliminated by overnight incubation with BAPTA-AM (10 μM), suggesting that the currents were dependent on intracellular Ca 2+ increase. Thus the plant extracts activate the typical oscillatory Ca 2+ -dependent Cl – currents generated in the Xenopus oocyte membrane more probably via a mechanism that involves release of Ca 2+ from intracellular reservoirs. These observations suggest that Xenopus oocyte electrophysiological recording constitutes a suitable assay for the study of the mechanisms of action of herbal medicines.