Characterization of Volatile Compounds in Four Different Rhododendron Flowers by GC×GC-QTOFMS

Abstract

Volatile compounds in flowers of <i>Rhododendron delavayi</i>, <i>R. agastum</i>, <i>R. annae</i>, and <i>R. irroratum</i> were analyzed using comprehensive two-dimensional gas chromatography-mass spectrometry (GC×GC) coupled with high-resolution quadrupole time-of-flight mass spectrometry (QTOFMS). A significantly increased number of compounds was separated by GC×GC compared to conventional one-dimensional GC (1DGC), allowing more comprehensive understanding of the volatile composition of <i>Rhododendron</i> flowers. In total, 129 volatile compounds were detected and quantified. Among them, hexanal, limonene, benzeneacetaldehyde, 2-nonen-1-ol, phenylethyl alcohol, citronellal, isopulegol, 3,5-dimethoxytoluene, and pyridine are the main compounds with different content levels in all flower samples. 1,2,3-trimethoxy-5-methyl-benzene exhibits significantly higher content in <i>R. irroratum</i> compared to in the other three species, while isopulegol is only found in <i>R. irroratum</i> and <i>R. agastum</i>.