A new sesquiterpene lactone from the leaves of Panax vietnamensis Ha et Grushv. (Vietnamese ginseng)

Panax vietnamensis (Vietnamese ginseng, Ngoc Linh ginseng) is an endemic Panax species of Vietnam. From the methanol extract of the leaves of Panax vietnamensis, five compounds (1–5) were isolated, including one new sesquiterpene lactone such as panaxolide (1) and four known compounds. The structures of the compounds (1-5) were elucidated by spectral techniques such as 1 D NMR (1H NMR, 13C NMR), 2 D NMR (COSY, HSQC, HMBC, NOESY) and mass spectrometry. The absolute configuration of 1 was determined based on the Cotton effects in the CD spectrum. All of the five compounds were screened for their in vitro growth inhibitory activities against cancerous cells (HepG2) and normal cells (fibroblast) using the SRB assay. Panaxolide (1) showed the highest potential for the growth inhibition of cancerous cells HepG2 with the IC50 values of 63.8 μM.