Volatile compounds in flowers of Rhododendron delavayi, R. agastum, R. annae, and R. irroratum 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 Rhododendron 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 R. irroratum compared to in the other three species, while isopulegol is only found in R. irroratum and R. agastum.
Characterization of Volatile Compounds in Four Different Rhododendron Flowers by GC×GC-QTOFMS
