Nerve growth factor-potentiating compounds from Picrorhizae Rhizoma

Abstract

A crude methanol extract of Picrorhizae Rhizoma, the dried underground parts of Picrorhiza scrophulariiflora PENNELL, has been shown to potentiate the nerve growth factor (NGF)-induced neurite outgrowth from PC12D cells. The methanol extract was partitioned between ethyl acetate and water. The NGF- potentiating activity was observed in the ethyl acetate fraction. The ethyl acetate solubles were fractionated by silica get chromatography, monitoring the NGF-potentiating activity to give two iridoid glycosides, picrosides I and II. Picrosides did not exhibit neurotrophic activity but caused a marked enhancement of the NGF-mediated neurite outgrowth from PC12D cells. The pharmacological data suggest that picrosides I and II enhance neurite outgrowth from PC12D cells, probably by amplifying a step in the NGF- receptor-mediated intracellular signaling pathway.