Schekwanglupaside C, a new lupane saponin from Schefflera kwangsiensis, is a potent activator of sarcoplasmic reticulum Ca2+-ATPase

Abstract

Schefflera kwangsiensis Merr. ex H.L. Li (Araliaceae) is a widely used traditional Chinese medicine for pain management in the clinic. In the present study, we isolated a previously undescribed lupane saponin, designated as schekwanglupaside C (Sch C) from the ethanolic extract of S. kwangsiensis. The structure of Sch C was determined by comprehensive spectroscopic and spectrometric analyses and chemical degradation. In primary cultured cortical neurons, Sch C altered the pattern of spontaneous Ca²⁺ oscillation (SCO) with a slight increase in the frequency of SCO right after addition and a gradual decrease in the frequency and amplitude of SCO, that dynamic change mimicked by an activator of sarcoplasmic reticulum Ca²⁺-ATPase (SERCA). The IC₅₀ values for Sch C suppression of the frequency and amplitude of SCO were 1.75 and 2.51 μM, respectively. Furthermore, we demonstrated that Sch C is a potent SERCA activator (EC₅₀ = 1.20 μM). Given the pivotal role of SERCA in the progression of neuropathic pain and neurodegenerative diseases, Sch C represents a new drug lead compound to develop the treatment of neuropathic pain and Alzheimer's disease.

Keywords: Ca(2+); Lupane saponin; S. kwangsiensis; Sarcoplasmic reticulum Ca(2+)-ATPase; Schekwanglupaside C.