To elucidate the chemical material basis of Rhododendron nivale, this study comprehensively used various chromatographic techniques to isolate and obtain five new meroterpenoid enantiomers(1a/1b-5a/5b) from the ethyl acetate extract of R. nivale. A variety of spectral analytical methods, such as high-resolution mass spectrometry(HRMS), nuclear magnetic resonance spectroscopy(NMR), and infrared(IR) spectrum, were used to evaluate the structure, combined with the measurement and calculation of electronic circular dichroism(ECD). The new compounds 1a/1b-4a/4b were named as(±)-nivalones A-B(1a/1b-2a/2b) and(±)-nivalnoids C-D(3a/3b-4a/4b), along with one known enantiomer(±)-anthoponoid G(5a/5b). Human neuroblastoma cells(SH-SY5Y cells) induced by hydrogen peroxide(H_2O_2) were used as oxidative stress models to evaluate the protective activity of the isolated compounds against oxidative damage to nerve cells. It was found that compounds 2a and 3a had a certain protective effect on nerve cells against H_2O_2-induced oxidative damage at concentrations of 50 μmol·L~(-1), which increased the cell survival rate from 44.02%±2.30% to 67.82%±1.12% and 62.20%±1.87%, respectively. Other compounds did not show a significant ability to protect cells from oxidative damage. These findings enrich the chemical constituents of R. nivale and provide valuable information for identifying the structure of its meroterpenoids.
Keywords: Rhododendron nivale; enantiomers; meroterpenoids; neuroprotective activity; oxidative damage.