Triterpenoids and a sterol from the stem‐bark of Styrax japonica and their protein tyrosine phosphatase 1B inhibitory activities

Abstract

Five pentacyclic triterpenoids (1–5) and a sterol (6) were isolated from the stem‐bark of Styrax japonica. The six compounds, 1–6, were determined to be 3β‐acetoxy‐28‐hydroxyolean‐12‐ene (1), 3β‐acetoxyolean‐12‐en‐28‐acid (2), 3β‐acetoxyolean‐12‐en‐28‐aldehyde (3), 3β‐acetoxy‐17β‐hydroxy‐28‐norolean‐12‐ene (4), taraxerol (5) and stigmasterol (6), respectively, by spectroscopic means, including the 2D‐NMR technique. Compound 4 is a newly discovered natural compound. The protein tyrosine phosphatase 1B (PTP1B) inhibitory activities of the isolated compounds (1–6) were determined in vitro. Among the isolated compounds, 3β‐acetoxyolean‐12‐en‐28‐acid (2) and 3β‐acetoxyolean‐12‐en‐28‐aldehyde (3) had the most potent inhibitory PTP1B activity, with IC50 values of 7.8 and 9.3 µm, respectively. Copyright © 2008 John Wiley & Sons, Ltd.